Log all formatter error messages in a csc-style

[JoeRobich]

Resolves #953

Example msbuild output:

~/output-test> dotnet build /p:EnforceCodeStyleInBuild=true
Microsoft (R) Build Engine version 16.9.0-preview-21064-01+995458447 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  Restored /Users/joeyrobichaud/output-test/output-test.csproj (in 95 ms).
  You are using a preview version of .NET. See: https://aka.ms/dotnet-core-preview
/Users/joeyrobichaud/output-test/Test0.cs(10,13): warning CS0219: The variable 'count' is assigned but its value is never used [/Users/joeyrobichaud/output-test/output-test.csproj]
/Users/joeyrobichaud/output-test/Test0.cs(8,9): error IDE0007: use 'var' instead of explicit type [/Users/joeyrobichaud/output-test/output-test.csproj]
/Users/joeyrobichaud/output-test/Test0.cs(9,9): error IDE0007: use 'var' instead of explicit type [/Users/joeyrobichaud/output-test/output-test.csproj]
/Users/joeyrobichaud/output-test/Test0.cs(10,9): error IDE0007: use 'var' instead of explicit type [/Users/joeyrobichaud/output-test/output-test.csproj]

Build FAILED.

Example dotnet format diagnostic output

  The dotnet format version is '5.1.0-dev'.
  The dotnet runtime version is '6.0.0-alpha.1.21064.11'.
  The dotnet CLI version is '6.0.100-alpha.1.21065.7'.
  Using MSBuild.exe located in '/usr/local/share/dotnet/sdk/6.0.100-alpha.1.21065.7/'.
  Formatting code files in workspace '/Users/joeyrobichaud/output-test/output-test.csproj'.
  Loading workspace.
  Project output-test is using configuration from '/Users/joeyrobichaud/output-test/.editorconfig'.
  Project output-test is using configuration from '/Users/joeyrobichaud/output-test/obj/Debug/net5.0/output-test.GeneratedMSBuildEditorConfig.editorconfig'.
  Project output-test is using configuration from '/usr/local/share/dotnet/sdk/6.0.100-alpha.1.21065.7/Sdks/Microsoft.NET.Sdk/analyzers/build/config/AnalysisLevel_5_Default.editorconfig'.
  Complete in 3612ms.
  Determining formattable files.
  Complete in 388ms.
  Running formatters.
  Running Code Style analysis.
  Determining diagnostics...
  Running 4 analyzers on output-test.
/Users/joeyrobichaud/output-test/Test0.cs(8,9): error IDE0007: use 'var' instead of explicit type [/Users/joeyrobichaud/output-test/output-test.csproj]
/Users/joeyrobichaud/output-test/Test0.cs(9,9): error IDE0007: use 'var' instead of explicit type [/Users/joeyrobichaud/output-test/output-test.csproj]
/Users/joeyrobichaud/output-test/Test0.cs(10,9): error IDE0007: use 'var' instead of explicit type [/Users/joeyrobichaud/output-test/output-test.csproj]
/Users/joeyrobichaud/output-test/Test0.cs(10,13): warning CS0219: The variable 'count' is assigned but its value is never used [/Users/joeyrobichaud/output-test/output-test.csproj]
  Complete in 1891ms.
  Analysis complete in 1891ms.
  Complete in 2139ms.
  Formatted code file '/Users/joeyrobichaud/output-test/Test0.cs'.
  Formatted 1 of 4 files.
  Format complete in 6139ms.

Example dotnet format whitespace output

  The dotnet runtime version is '6.0.0-alpha.1.21064.11'.
  Using MSBuild.exe located in '/usr/local/share/dotnet/sdk/6.0.100-alpha.1.21065.7/'.
  Formatting code files in workspace '/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj'.
  Loading workspace.
  Project unformatted_project is using configuration from '/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/.editorconfig'.
  Project unformatted_project is using configuration from '/Users/joeyrobichaud/Source/format/.editorconfig'.
  Complete in 1947ms.
  Determining formattable files.
  Complete in 341ms.
  Running formatters.
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs(5,3): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs(6,3): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs(7,5): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs(8,5): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs(9,7): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs(10,5): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs(11,3): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs(5,3): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs(6,3): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs(7,5): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs(8,5): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs(9,7): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs(10,5): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs(11,3): error WHITESPACE: Fix whitespace formatting. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs(12,2): error FINALNEWLINE: Fix final newline. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs(12,2): error FINALNEWLINE: Fix final newline. [/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/unformatted_project.csproj]
  Complete in 384ms.
  Formatted code file '/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/other_items/OtherClass.cs'.
  Formatted code file '/Users/joeyrobichaud/Source/format/tests/projects/for_code_formatter/unformatted_project/Program.cs'.
  Formatted 2 of 6 files.
  Format complete in 2673ms.