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.

.Net - .NET

Since the given members are obsolete and will cause a build error if used, 
it's just better if they aren't shown at all.

Fixes #33546

* Fixes #33601

* Respond to feedback

* Restrict to only trigger if identifier is in selection

* Respond to feedback

* respond to feedback

* Respond to feeback

Fixes #33829

* added ability to clear all diagnostics reproted from a IDiagnosticUpdateSource

previously IDiagnosticUpdateSource has to clear each diagnostics it reported group by group. that was fine for IDiagnosticUpdateSource that supports incremental update, but some source such as EditAndContinue doesn't support incremental update since their errors (emit errors) come and go as a bulk (whole project). when they update, they need to update everything. so tracking things in group for incremental update is unnecessary for such source.

the new API (Source.Cleared) make it easy for source to clear all diagnostics at once it produced.

* addressing PR feedbacks

* Enable OOP features by default.

* Removing unused function.

* conflicts

* Fixes 33602

* respond to comments

* Fixes 14077

* Respond to feedback

* More tests

* Add FallbackNamingRule for parameters

* Fix default parameter naming rule

* Use parameter naming style, add tests