Merge dev16.1-preview2 to dev16.1-preview2-vs-deps

Implement import completion for types

* [WIP] first draft to move to new code lens API

* rename SemanticChangeTracker to WorkspaceChangeTracker since reference counter can change without semantic changes (such as method body change causing reference to be added or removed)

* created new dll for new code lens OOP. can't use existing VS dlls since it has more dependencies than what CodeLens can provide. we don't control code lens OOP so new dll with only depdencies required for code lens.

* fix resource id name

* pass in cancellation token on place it is missing

* ServiceHubServiceBase no longer expose Rpc directly

* address PR feedbacks

* fixed build break due to the merge

* fixed nuget version conflicts

* fixed designtime dll issue

* moved to new APIs that fix staled spans

* updated to versions suggested by editor team

* PR feedbacks

* Addressed PR feedbacks

Add command handler and tests for toggle line comment.

Merge branch 'ignoreCOmpletionItemSpan' of https://github.com/CyrusNajmabadi/roslyn into TypeImportCompletion2

Merge branch 'completionItemDoc' of https://github.com/CyrusNajmabadi/roslyn into TypeImportCompletion2

remove

revert

simplify

simplify

simplify

simplify

remove stale comment'

This avoids getting full compilation from everything project references

Merge dev16.1-preview2 to dev16.1-preview2-vs-deps