This depends on VS APIs that we don't have open source yet, and we
don't need the feature for now in VS for Mac.

Fixes dotnet/roslyn#23192.

This lived in EditorFeatures.Next since it depended on Dev15 features,
but EditorFeatures is now Dev15 only so we can move this.

* moving naming styles types into the workspace layer.
Teaching abstract options serialization service about naming styles.

* Implementing naming styles support for editorconfig

* responding to david's PR feedback

* responding to Jason's feedback

* responding to Jason's feedback part 2

* addressing the latest set of comments from David

* addressing Jason's comments

* addressing Kevin's comments

Reporting this to the error list is something we can consider doing
later.

- Don't expose the lambda back out
- Make a default case so you don't have to specify a lambda at all
  for common things like bool or int