Synchronize AnalyzerConfig documents when creating OOP solutions

Ensure we set _isSubscribedToSolutionEvents

Fixes #31685

* Add reproducer for #34872

* Fix bug and add test

* WIP

* Test similar scenario in VB

* Add void check in ClassifyConversionFromType, update tuple tests

* Cleanup

If we don't set this, we'll subscribe to solution events multiple times
which isn't great. Our event handler is idempotent so it'll still do
the right thing, but we'll just be wasting extra time processing
notifications that won't do anything.

Fixes https://github.com/dotnet/roslyn/issues/35372

* Don't emit readonly attributes on members within readonly structs

* Check ContainingType.IsReadOnly before EnsureIsReadOnlyAttributeExists just for consistency