Make return type of classifications handler object to avoid issues with dynamic usage on internal types.

Merge master to features/lspSupport

* Remove RoslynProjectType

* Remove ToolsVersion, namespace from Project tags

* Remove updating of MSBuildAllProjects

* Update BuildBoss

* Delete DeployTooolsetCompiler

Merge release/dev16.1 to master

 Hide dependency on VsInteractiveWindow package from Microsoft.VisualStudio.LanguageServices package (#35262)

* Hide dependency on VsInteractiveWindow package from Microsoft.VisualStudio.LanguageServices package

* FIx reference

* Comment

(cherry picked from commit c421f124)

* Permit stackalloc in nested contexts. (#28969)
Fixes #26759

Update yml files for `release/*` branches

Update PublishData for "release/" branch prefix

* Update dependencies from https://github.com/dotnet/arcade build 20190407.1

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19207.1

* Update dependencies from https://github.com/dotnet/arcade build 20190409.2

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19209.2

* Update dependencies from https://github.com/dotnet/arcade build 20190410.7

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19210.7

* Update dependencies from https://github.com/dotnet/arcade build 20190411.2

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19211.2

* Update dependencies from https://github.com/dotnet/arcade build 20190412.2

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19212.2

* Update dependencies from https://github.com/dotnet/arcade build 20190413.2

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19213.2

* Update dependencies from https://github.com/dotnet/arcade build 20190414.2

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19214.2

* Update dependencies from https://github.com/dotnet/arcade build 20190415.12

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19215.12

* Update dependencies from https://github.com/dotnet/arcade build 20190417.1

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19217.1

* Update dependencies from https://github.com/dotnet/arcade build 20190418.1

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19218.1

* Update dependencies from https://github.com/dotnet/arcade build 20190418.4

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19218.4

* Update dependencies from https://github.com/dotnet/arcade build 20190418.7

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19218.7

* Update dependencies from https://github.com/dotnet/arcade build 20190422.2

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19222.2

* Update dependencies from https://github.com/dotnet/arcade build 20190423.2

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19223.2

* Use Arcade CoreXT package support

* Update dependencies from https://github.com/dotnet/arcade build 20190424.9

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19224.9

* Fix signing

* Update dependencies from https://github.com/dotnet/arcade build 20190425.5

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19225.5

* Update dependencies from https://github.com/dotnet/arcade build 20190426.3

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19226.3

* Update dependencies from https://github.com/dotnet/arcade build 20190429.8

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19229.8

* Update dependencies from https://github.com/dotnet/arcade build 20190430.6

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19230.6

Merge dev16.1 to master

This change is required in order to enable running on non-desktop TFM tests from VS test explorer window.

Fixes #29956

Also introduce a helper `TypeSymbol.IsVoidType()`

Fix broken links in Language Feature Status

* Additional Nullability checks for deconstruction:
- Check 'this' param for extension deconstruct
- Re-infer the argument types for generic extension deconstruct
- Update the deconstruction method in instance cases
- Update return type with visited arguments
- Update tests