* Clean up string resources, use Arcade resx generator

* CodeLens resources


* Use NET20 instead of NETFX20

This removes the hard dependency on the editor packages so we can
still support loading in 16.3. The unit tests must be disabled that
depend on the new support, but everything else will continue to
function.

* Remove RoslynProjectType

* Remove ToolsVersion, namespace from Project tags

* Remove updating of MSBuildAllProjects

* Update BuildBoss

* Delete DeployTooolsetCompiler

* Revert "Revert "Interactive projects refactoring (#29069)""

This reverts commit e0a8124f.

* Fix bad merge

This reverts commit 41fb51d2.

Remove Repl projects

Remove Microsoft.VisualStudio.InteractiveServices project

Remove Microsoft.CodeAnalysis.InteractiveEditorFeatures

Rename InteractiveEditorFeatures to EditorFeatures.Wpf

Remove empty resource files

Reduce InteractiveFeatures dependencies

Merge InteractiveComponents content into Roslyn.VisualStudio.Setup VSIX

Rename InteractiveFeatures to InteractiveHost

Hook fatal error handlers

Workaround warning CS1574

Exclude CreateTemplateManifestsCacheFile

Do not include satellite assemblies in DesktopHost directory

Remove VB interactive menu item

Delete VisualBasic.EditorFeatures.Wpf

Delete more unused VB interactive code

* Remove RuntimeIdentifier specification

* Arcade directory layout

* Move xunit package references to Roslyn.Toolsets.Xunit.targets

* Remove dependency on Microsoft.NET.Test.Sdk

The C# syntax tests were missing a reference to xunit.runner.visualstudio
which prevented them from working in the Test Explorer in 15.8 Preview.
Rather than just adding a reference to this one test, I've added a reference
to the root test utilities project, that almsot every test references, and
deleted the explicit references in the test leaf projects. This should
hopefully be a more robust method of using the XUnit VS test adapter.

Even though Roslyn can only every be deployed where at least net461 or netcoreapp2.0 is available Roslyn cannot depend on netstandard2.0 assemblies. This is due to the setup of Visual Studio which has a minimum target of net46 and hence only deploys netstandard1.3 facades. In order to prevent netstandard2.0 versions of NuGet references to deploy, at build or test, we must limit the desktop target framework used in our projects to net46.

There is nothing functionally wrong with having our tests target net461. At the same time though it would mean our tests were running against the netstandard2.0 version of references, such as System.Collections.Immutable, which is not what we deploy against. Hence not testing what we ship which creates a small but real hole.

Closes #25560

The combination of the minified MSBuild syntax and Directory.Build.props
/ targets file will change when in the build process our central build
files are executed. For instance Imports.targets will now be run much
later in the build after Sdk.targets. Where before, when it manually
invkoed Sdk.targets it was able to run both before and after it.

To keep our build functioning the same way we need to move around some
of the logic within our build files so that it executes in the same
relative order as it did before

This primarily moves us to the 2.2.0 version of xunit. In order to make
that transition though a number of other changes needed to happen as
well:

1. Needed to move our desktop target to 4.6.1. This should've been
required some time ago but we were essentially depending on bugs in the
SDK / NuGet.
1. Remove the DeployCoreClrTestRuntime project. This entire idea
depended on having the xunit.console.netcore package. This has since
been deleted and doesn't work with the 2.0 SDK.
1. Remove the deploy compiler tools project. Can just use dotnet exec
now and that's much more efficient.
1. Resolve a new ambiguity with KeyValuePair. A helper of ours now
exists in netcoreapp2.0.

I fully expect a number of Jenkins legs to fail with this change: build
correctness, coreclr and ubuntu. But I want to validate our other legs
and am still trackind down answers needed to fix the others.

In the new SDK we no longer have a need for ProjectGuid. This change
will:

- Remove ProjectGuid from project files
- Remove Name + Project items from ProjectReference entries
- Change BuildBoss to enforce both of these items

Migrated the remainder of our code base to use the new SDK via the
ConvertPackageRef tool.

https://github.com/jaredpar/ConvertPackageRef

This is an automated migration of our project files to the new SDK /
PackageReference.  It is done using the tool located here:

https://github.com/jaredpar/ConvertPackageRef

This project is no longer necessary.  It used to help us get TDD working fine in Visual Studio.  That's no lonegr needed with the recent build cleanup.  TDD still functions with this project removed.