Comment out some imports in CodeStyle layer. These will be reverted with https://github.com/dotnet/roslyn/pull/41363

Extracts out the changes to core Workspace changes from https://github.com/dotnet/roslyn/pull/41363.

fix for language code capitalization

This is not a user facing string, so must not be localized. Additionally, with https://github.com/dotnet/roslyn/pull/38886, we now support bulk severity configuration in editorconfig based on diagnostic category, so the string ought to be a non-localized constant without any spaces.

Adds the definitions for the nullable attributes and creates an
annotated Debug.Assert

Closes #36930
Closes #38587