Split analyzers and code fixes into separate projects

[MrJul]

What does the pull request do?

This PR splits the Analyzers project into three:

• Analyzers.CSharp
• Analyzers.VisualBasic
• Analyzers.CodeFixes.CSharp

Types for code fixes or other languages aren't guaranteed to be referenced while compiling outside IDEs. We didn't have any trouble before because we aren't blindly using those, but let's be explicit.

This follows the recommendation from Microsoft, see RS1038 for details.

[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0060939-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[maxkatz6]

It's just different assemblies, still kept in the single nuget package, right?
Feels excessive, and I don't remember if I saw many projects do that. But since Microsoft recommends it, I am good.

[MrJul]

It's just different assemblies, still kept in the single nuget package, right?

Yes, they're all merged into our main Avalonia package at build time.

Feels excessive, and I don't remember if I saw many projects do that. But since Microsoft recommends it, I am good.

It's a fairly recent public recommendation from the analyzers afaict, but Microsoft has been using it for a while:

• Winforms: https://github.com/dotnet/winforms/tree/main/src
• VS Threading: https://github.com/microsoft/vs-threading/tree/main/src
• ASP.NET Core: https://github.com/dotnet/aspnetcore/tree/main/src/Framework/AspNetCoreAnalyzers/src

[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0061273-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]