Linux Support: from experimental to 100% 🚀

[art-divin]

Description

This issue is for tracking purposes.

Currently, there are a few features disabled for the sake of supporting Linux:

1. Code generation for Sourcery codebase - it generates Equatable.generated etc. -> which were moved to class definitions due to the fact that under Linux it is not possible to override a method from an extension (@objc is unavailable). Even in Darwin variant, it looks odd, though, and I want to address this in a future PR, where I would inject generated code into specific areas of the class definitions like it is now. For that, I need to research template system a little bit more. I see this is done already for Codable methods.
2. On Linux there's a number of issues with swift compiler. There's one crash from swift compiler which breaks a number of tests. Removing #if canImport(ObjectiveC) statements piece by piece would bring stability to Sourcery on Linux and in future on Windows.
3. DynamicMemberLookup conformance must be made using code generation and automated for Sourcery codebase.
4. Release process does not work 100% as expected - probably needs to be moved to GH actions.
5. Documentation includes Linux files, which should be ignored to avoid duplication
6. Documentation includes hash and diff functions, which should not be included into the doc
7. Missing tests that cover using a compiled Sourcery when it is packaged in release mode. Context: Issue when running sourcery from binary #1202
8. Missing DynamicMemberLookup conformance of GenericParameter type. Context: Added generic requirements and generic parameters to Subscript #1242

This issue will be updated and is a follow up of #306.