Set version to '16.6'

LOC CHECKIN | Microsoft/vs-threading master | 20200207

Merge pull request microsoft#582 from AArnott/addAnalyzerPkgDependency

Add vs-threading dependency on the analyzers

Merge pull request microsoft#576 from AArnott/STMTA_Cancellation

Ensure JTF.SwitchToMainThreadAsync always throws when canceled

Merge pull request microsoft#570 from AArnott/fix569

Throw synchronously from STMTA if token is precanceled off the main thread

Merge pull request microsoft#575 from AArnott/fixVSTHRD003

VSTHRD003 fixes: more good and less bad

Merge pull request microsoft#574 from AArnott/fixVSTHRD003

Remove VSTHRD003 warnings for readonly tasks defined in another assembly

Merge pull request microsoft#565 from yhvicey/yiwwan/Fix431

Fix VSTHRD200 when using IAsyncEnumerable

Merge pull request microsoft#558 from AArnott/fix557

Avoid C# syntax that's toxic to .NET Native compilers

Merge pull request microsoft#524 from AArnott/sosthreadingtools_depen…

…dency

Package up Microsoft.Diagnostics.Runtime.dll with SosThreadingTools