[RFC FS-1075] Improve interop to C# nullable-typed optionals (dotnet#7989)

* add test cases we need to make work

* cleanup method call argument processing

* update for new cases

* update tests

* compat Nullable allowed

* reduce diff

* fix mistake with byrefs

* update error message

* trigger CI

* add version tests

* mnimize diff

* mnimize diff

* remove assert

* minor updates for code review

* fix overloading change of behaviour

Co-authored-by: Phillip Carter <[email protected]>

Author: 2 people

Completion/SignatureHelp.fs

@@ -168,6 +168,7 @@ type internal FSharpSignatureHelpProvider
             let prefixParts = 
                 [| TaggedText(TextTags.Method, methodGroup.MethodName);  
                    TaggedText(TextTags.Punctuation, (if isStaticArgTip then "<" else "(")) |]
+
             let separatorParts = [| TaggedText(TextTags.Punctuation, ","); TaggedText(TextTags.Space, " ") |]
             let suffixParts = [| TaggedText(TextTags.Punctuation, (if isStaticArgTip then ">" else ")")) |]