Merge release/dev16.6-preview1 to master

Update GetOption to return the default option value

Make it simple to generate auto-properties from the SyntaxGenerator API.

Merge release/dev16.5 to release/dev16.6-preview1

- Microsoft.DotNet.Arcade.Sdk - 5.0.0-beta.20129.1

Switch more code from ISyntaxFactsService to ISyntaxFacts

* Add overload used by Razor via IVT back

* Update src/Workspaces/Core/Portable/Workspace/Solution/DocumentInfo.cs
Co-Authored-By: NJason Malinowski <jason.malinowski@microsoft.com>
Co-authored-by: NJason Malinowski <jason@jason-m.com>

Follow up to https://github.com/dotnet/roslyn/pull/42015/files#r385741503
This change allows couple of things:
1. Make C# and VB ISyntaxFactsService implementation private nested types.
2. Aid future porting of analyzers to CodeStyle layer by moving bunch of our analyzers/fixers/helpers to use ISyntaxFacts as opposed to ISyntaxFactsService, latter is not available in CodeStyle analyzer layer.

- Microsoft.DotNet.Arcade.Sdk - 5.0.0-beta.20128.3

Remove solution size tracking from Roslyn.

Use strongly-typed return values in PreviewFactoryService

Enable VSTHRD200 (Use Async naming convention) in production code

Use pooling pattern for ArrayBuilders.

Move SyntaxFacts service down to CompilerExtensions shared project

Merge remote-tracking branch 'origin/release/dev16.6-preview1' into merges/release/dev16.5-to-release/dev16.6-preview1

Add OptionSet.AsAnalyzerConfigOptions

Add UnitTests for Issue #38513

Switch to an easier pooling model for pooled collections in the IDE.

Don't suggest using named arguments for implicit Index and Range indexers

* Failing tests for writing with a range starting > 0

* Fixed SourceText.Write for spans that don't start at 0

* Math.Min is redundant with CheckSubSpan

* TextSpan guarantees that Start >= 0

* TextSpan guarantees that Start <= End

* Assert is preferred over comment

Move back the ContextQuery related extensions and corresponding SyntaxFact APIs up to the shared WorkspaceExtensions project

Move ISyntaxKindsService language service in shared layer

Prohibit C# 8 index and range usage in expression trees