[VS Code] [Cohosting] C# code actions with fix all support don't work

Roslyn has custom commands in VS Code that handle fix all in code actions, and that system doesn't work for Razor documents.

The command routes the request to Roslyn's code action resolve endpoint, so we probably just need to detect that the code action is happening in a Razor document, and route the request through to Razor. In theory we would do this by wrapping the data in the request and adding a document, and whatever else Razor requires, then the request would be routed to Razor, unwrapped, and it would route to the Roslyn code action resolve endpoint.

Start by tracing the VS Code custom commands that route code actions to Roslyn's code action resolve endpoint, then compare the request path for Razor documents. Done means C# fix-all code actions work in Razor documents through the Razor-to-Roslyn routing described in the issue.