Remove Avalonia.ReactiveUI.Events

[rstm-sf]

What does the pull request do?

Remove Avalonia.ReactiveUI.Events

What is the current behavior?

Build problems with Pharmacist when upgrading sdk to net5

What is the updated/expected behavior with this PR?

Remove Avalonia.ReactiveUI.Events

How was the solution implemented (if it's not obvious)?

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/Avaloniaui.net with user documentation

Breaking changes

Avalonia.ReactiveUI.Events will no longer supports. Use Pharmacist.MSBuild instead. How to use it? https://github.com/reactiveui/Pharmacist#msbuild

cc: @worldbeater Can a better description be made for the end of support?

Fixed issues

[worldbeater]

Avalonia.ReactiveUI.Events is just a package that contains precompiled .Events(), so folks don't have to generate the wrappers on their own. Migrating from Avalonia.ReactiveUI.Events to Pharmacist.MsBuild should be quite simple, e.g. instead of referencing Avalonia.ReactiveUI.Events folks should reference Pharmacist.MsBuild as such:

And then rebuild the project:

dotnet build

After doing that, the events will generate automatically for Avalonia assemblies.
See also: https://github.com/reactiveui/pharmacist#nuget-packages

[worldbeater]

Assuming ICSharpCode.Decompiler seems to be broken on Linux machines with .NET 5 installed, and this issue is blocking Avalonia .NET 5 upgrade, probably worth removing Avalonia.ReactiveUI.Events and recommending the direct consumption of Pharmacist.MsBuild as stated above.

Also assuming the Avalonia.ReactiveUI.Events package is already shipped to NuGet, the removal of this package from the main repository shouldn't even be much of an issue. The generated package is backward-compatible and is probably moving to its own repository in the future.