Co-authored-by: NJason Malinowski <jason@jason-m.com>

Co-authored-by: NJason Malinowski <jason@jason-m.com>

Co-authored-by: NJason Malinowski <jason@jason-m.com>

Co-authored-by: NJason Malinowski <jason@jason-m.com>

Co-authored-by: NJason Malinowski <jason@jason-m.com>

Relax dedupe logic in code fix service

Fixes #44663.

Relax the de-duplication logic in CodeFixService to allow a code fix provider to register multiple code actions with same equivalence key for backward compatibility. See https://github.com/dotnet/roslyn/issues/44553#issuecomment-636305256 for details

Add unit test to demonstrate the breaking change introduced in #41768, and described in https://github.com/dotnet/roslyn/issues/44553#issuecomment-636305256

Verified the test failed without any product change.

Fix equivalence key for Populate-Switch

Merge master to features/function-pointers

Improve performance of SyntaxTreeIndex checksum computation.

Fix wrong reporting for removing parenthesis for stackalloc

* RemoveHostClientProvider

* Do not start ServiceHub in command line mode

* Unused usings

* CreateConnection can no longer return null

* Connection refactoring

* Feedback

* Feedback

* Workaround for CodeLens issue

* Address NuGet PackageInstall failure

* Remove NuGet workaroud fixed in 15.9

* Fix potential hang

Merge master into features/function-pointers

* dotnet/master:
  Update error code in ConvertIfToSwitch test
  Don't specify OpenClose, default value is false
  Wait for callbacks to complete before returning
  Tell lsp client not to send us open/close notifications

Address final prototype comments.

Wait for callbacks to complete before returning

Update error code in ConvertIfToSwitch test

Tell lsp client not to send us open/close notifications