…mmon code

…letionItemProvider to common layer.

…ded by RemoteCompletionService

Switch passed in and returned types from Roslyn to VS Platform LSP types since that's what all of the common completion code in the Workspaces layer uses. We will need to convert returned Roslyn completion items to VS platform LSP completion items.

…et used in cohosting

…e workspaces layer (to be used in cohosting later)

…g HTML completion item labels to RazorCompletionListProvider

…r and minor cleanup

… layer and use it in cohost completion request

Also simplifying parameters passed to the response re-writers to only what's needed.

…hooked up and we are getting VSInternalCompletionContext in CompletionParams

…ng them

They all already checked (or should've checked) for language and were operating on either C# or HTML, never on both. HTML re-writer will get called from the client and can be much simpler. In cohosting it doesn't make sense to have them all in one list since C# will get called in OOP and HTML on the client (in VS).

… it up in cohosting

Renamed some fields and variables dealing with "add snippets" options and added comments. We currently have two options that mean "add snippets" - one for the delegated completion, and one for Razor completion. The values of those don't correlate. The Razor one is always true in LSP and Cohost, always false for legacy editor. The delegation one actually depends on the position.

… cohost

Also adding a snippet completion provider test and markup transition test

…ces test projects

The tests were left behind (some in this PR, some in prior PRs) when the code was moved to Workspaces layer. This commit addresses most of them other than in Delegation subworkspace

We had inconsistent handling of null completion item labels between our response re-writers. Some handled null labels, others would through. Since label shouldn't be null (non-nullable), I adjusted the tests not to use null labels.

Also the tests previously passed because they created DelegatedCompletionListProvider with only a selected DelegatedResponseRewriter. Now the DelegatedCompletionHelper will apply all response re-writers for the correct language (either C# or HTML), which is what the product actually does, so I feel that's fine. It exposed these test failures due to inconsistent null label handling

… in RemoteCompletionService

Switching AllTriggerCharacters to string[] since we only use it for registration/capability data, which needs string[]. and we never do look ups via Contains. Also removing rendundant property and calculations in CompletionListProvider

… CR suggestion

…ggestion