Showing exceptions in the loading screen.

[dhoehna]

Please do not merge this PR until 05/17

Summary of the pull request

Caught exceptions in the loading screen when running a task, and un-caught exceptions in a task did not crash DevHome. But also DevHome did not notify the user of the failed task.

This PR adds this feature. :) These are reported to the user in the Loading Screen and are treated as a failed task.

References and relevant issues

Detailed description of the pull request / Additional comments

The logic to figure what message to show based on internal information is tightly coupled resulting in some duplicate code.

This PR contains the first steps in de-coupling internal information and the loading screen message.

The logic to keep executing messages at the bottom of the list was fragile. I upgraded this to use two ListViews. One for finished messages, and one for executing messages. This resulted in

1. Less code to write because two properties were removed.
2. Easier code to keep executing messages at the bottom of the loading screen.

Validation steps performed

Used Random to cause a crash in the loading screen and the clone task exception.
Specified argument was out of the range of valid values (window) is a crash in the code that runs a task.
`Value cannot be null (parameter 'Blah') is an un-caught crash inside CloneRepoTask.

Please ignore the "Can't clone because the location is not empty" errors when retying. This is because the exception in CloneRepoTask is thrown after the repo cloned.

PR checklist

• Closes Loading screen UI if a tasks exception isn't caught inside the task #629
• Tests added/passed
• Documentation updated

Movie!
https://github.com/microsoft/devhome/assets/2517139/14b9a23e-e4d1-43a0-8d2d-9502fc67d71a