The Quick Info service mostly defers to the symbol description service
to do most of it's work; the symbol description service takes a symbol
and a SemanticModel + position to build up the description of the
symbol, using that position for minimally qualifying types in some
cases. This position was also being used by the symbol description
service to see if the original invocation point was an await, and if so
it switched to special behavior to give a different message entirely;
there was some logic in Quick Info itself to also accomodate that.

This moves that special handling back up to Quick Info, and also does
a bit of a refactoring to include all of the decisions for what Quick
Info will show into a struct. This will be used later to help the LSIF
tool because it means if the two structs are equal than we know the
two Quick Info contents would the same and we can reuse it.

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

* upstream/master: (356 commits)
  Fix ConvertIfToSwitch on top-level statement (#44645)
  Test for not inferring inaccessible locals
  Don't sort fields & properties + comments
  Pass around a Document instead of SemanticModel+Workspace again
  Make GenerateInferredCallsiteExpressionAsync return just an Expression
  Getter control flow around GenerateInferredCallsiteExpressionAsync
  Pass around a Document instead of SemanticModel+Workspace
  Fix titles markdown in MetadataFormat.md
  Update dependencies from https://github.com/dotnet/arcade build 20200528.5 (#44660)
  Fix implementation of ISyntaxFacts.IsStatementContainer for top-level statements
  Follow up on 'Top-level statements' feature merge - pack error codes and feature ids. (#44636)
  Update FormattingEngineTriviaTests for top-level statements
  Add a registry storage location for StorageOptions.SQLiteInMemoryWriteCache
  Apply a hang mitigating timeout to InteractiveWithDisplayFormAndWpfWindow
  Update TotalClassifierTests for top-level statements
  Update SyntacticClassifierTests for top-level statements
  Update AutomaticLiteralCompletionTests for top-level statements
  Update RefKeywordRecommenderTests for top-level statements
  Update ReadOnlyKeywordRecommenderTests for top-level statements
  Adjust Roslyn.VisualStudio.IntegrationTests.CSharp.CSharpIntelliSense.CtrlAltSpaceOption unit-test with Top-level statements in mind.
  ...

Add Parameter option to populate call sites with available variables of the desired type