Move completion resolve code to common layer

[alexgav]

Summary of the changes

• Move completion resolve code that can be used from cohosting to the Workspaces layer
• This is the first step of cohosting completion resolve implementation

Fixes: #11157

Partial fix for #11101 (completing this shouldn't resolve the item)

[DustinCampbell]

Please don't move IProjectSnapshotManagerExtensions and MiscFilesHostProject to Workspaces. These can only be used in the Razor language server and moving them down would be a layering violation. completionitem/resolve can't take a dependency on an IProjectSnapshotManager, since that isn't available in co-hosting. Instead, code shared between the language server and co-hosting layers that need to access project information need to take an ISolutionQueryOperations. None of the code moved here will work in co-hosting without removing dependencies on IProjectSnapshotManager.

[alexgav]

IProjectSnapshotManager

Just so I understand - why do we have IProjectSnapshotManager in the Workspaces layer if it can only be used in the language server layer? Or is it only the misc project and extension methods that cannot be used outside of the language server layer?

[DustinCampbell]

IProjectSnapshotManager is used in the language server and Visual Studio layers. That's why it's in Workspaces. However, it isn't available in co-hosting. So, you'll need to break dependencies on IProjectSnapshotManager in any code you want to move from the language server to Workspaces and share with co-hosting. I had to do exactly the same thing for hover.

Taking a quick look, I think that what you probably need to do is the following:

1. Remove IProjectSnapshotManager from RazorCompletionItemResolver.
2. Update CompletionItemResolver.ResolverAsync(...) to take an ISolutionQueryOperations that RazorCompletionItemResovler's implementation can pass into ClassifiedTagHelperTooltipFactory and MarkupTagHelperTooltipFactory.

The extension methods being moved down here are for retrieving an ISolutionQueryOperations in the language server only. So, they should really stay in the language server. In co-hosting, RemoteSolutionSnapshot implements ISolutionQueryOperations, so it's easy to get ahold of. Here's an example of Go to Definition passing an ISolutionQueryOperations in co-hosting.

Didn't notice that MiscFileProject was moved. That is definitely the wrong thing to do.

[DustinCampbell]

This looks much better. Thank you!