Fixes #35203

1. Improve the message for unused value assignment diagnostic to make it clear that we are flagging an unnecessary assignment, not an unused variable
2. Add descriptions for unused value assignment and unused parameter diagnostics to allow users to specify special discard symbol names that are respected by the analyzer. There are various cases where user wants to retain unused parameters (signature compat, documentation) and unnecessary assignments to locals (ease of debugging), but do not want to blanket suppress these diagnostics.

Fixes #33994

* 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
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* 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
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* 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

Move to namespace allows a user to move all symbols in a context
to a different namespace, whether it's a new one or existing. This is
different from renaming a namespace as not all symbols in the namespace
are moved, only ones within the current document.

It relies on the IChangeNamespaceService implementation to do the heavy
lifting. Since the current implementation only supports C#, this new
feature will as well.

After this is checked in, when a user has the cursor inside a namespace
declaration that has no nested namespace declarations within it, a code
fix will be suggested to pop up a dialog and help the user choose a new
namespace.

This is a reworked version of #32616 targeting the dev16.0-preview3 branch.

Detect references to method/property in bound method group/property group using semantic model APIs. Also provide a different message for methods which have name only references.