Fixes #34678

* Add IsDeclaredReadOnly and IsEffectivelyReadOnly to public API

* Fix build. Add simple SemanticModel test.

* Fix Roslyn users of IMethodSymbol. Expand semantic model test.

* Fix visibility of MethodSymbol.vb members

* Implement ReadOnly method API in CodeGenerationConstructedMethodSymbol

* Cleanup usings and change NotImplementedException to ExceptionUtilities.Unreachable

* Simplify down to IMethodSymbol.IsReadOnly

* Fix IsReadOnly API for reduced extension methods. Test ref readonly ref
properties.

* Ensure that non-reduced extension methods are never 'readonly'

* Update doc

* Reduced extension methods are not declared readonly, they're effectively readonly.

* Remove unused copy of extension methods test source

* removed IEditorClassificationService that is marked obsolete since 2017 and bunch of other code that only existed for the IEditorClassificationService.

according to vso, only F# still has dependency so I talked to them to move to new API (IClassificationService) - https://devdiv.visualstudio.com/DevDiv/_git/DotNet-Source-Build-Tarball?path=%2Fsrc%2Ffsharp%2Fvsintegration%2Fsrc%2FFSharp.Editor%2FClassification%2FColorizationService.fs&version=GBmaster

and a bunch of clean up and move code that has no dependency to the editor to lower layers so that I can consume in razor scenario.

* added shim project for FSharp that has internal visible to FSharp editor

* merged https://github.com/dotnet/roslyn/pull/31941

* addressing PR feedback

* moved some type (such as DocumentSpan, ClassifiedSpan and etc) back to where fsharp has IVT to.

can't move those since partner team is using them and they don't have IVT to workspace layer for some reasons.

also, have put the IEditorClassificationService back and add a proxy in FSharp External Access so that it can still work until they remove all IVT.

- Do not generate implementation for sealed or static members.
- Do not generate implicit implementation for non-public members.
- Do not generate explicit implementation for inaccessible members.

* Fixes 33603 and 33623

* Respond to feedback

* Fix spelling/random characters
Co-Authored-By: Nchborl <chborl@users.noreply.github.com>

* Use IsEmpty property
Co-Authored-By: Nchborl <chborl@users.noreply.github.com>

* remove unneeded null check

* Configure await false
Co-Authored-By: Nchborl <chborl@users.noreply.github.com>

* refactor null check
Co-Authored-By: Nchborl <chborl@users.noreply.github.com>

* Respond to feedback and refactor

* Wrap long lines

* Update test comments
Co-Authored-By: Nchborl <chborl@users.noreply.github.com>

* Change .AsImmutableOrNull to .ToImmutableAndFree
Co-Authored-By: Nchborl <chborl@users.noreply.github.com>

* Fix test doc comments

* Apply suggestions from code review

Update doc comment
Co-Authored-By: Nchborl <chborl@users.noreply.github.com>

* Move EnC debug information reading to Features.

Encapsulate the logic in EditAndContinueMethodDebugInfoReader.

* Enable completion for modifiers allowed for interface members.

* Enable completion of keywords within an interface

- Enable type recommendation within interfaces.
- Do not recommend non-implementable members.

* Revert "Revert "Interactive projects refactoring (#29069)""

This reverts commit e0a8124f.

* Fix bad merge

This reverts commit 41fb51d2.

Remove Repl projects

Remove Microsoft.VisualStudio.InteractiveServices project

Remove Microsoft.CodeAnalysis.InteractiveEditorFeatures

Rename InteractiveEditorFeatures to EditorFeatures.Wpf

Remove empty resource files

Reduce InteractiveFeatures dependencies

Merge InteractiveComponents content into Roslyn.VisualStudio.Setup VSIX

Rename InteractiveFeatures to InteractiveHost

Hook fatal error handlers

Workaround warning CS1574

Exclude CreateTemplateManifestsCacheFile

Do not include satellite assemblies in DesktopHost directory

Remove VB interactive menu item

Delete VisualBasic.EditorFeatures.Wpf

Delete more unused VB interactive code