Skip a bunch of flaky integration tests

Merge dev15.3-preview2 to master

* Fix code gen for pattern switch with constant expression
Fixes #19731

* Add instrumentation for pattern switch with constant expression
Fixes #17090

* Incorrect code for generic pattern switch on a constant expression
Fixes #19734

Stop handling quickinfo

Add a test for an already fixed crash due to SemanticModel failing to locate the right binder. (#19995)

Related to https://devdiv.visualstudio.com/DevDiv/_workitems?id=445600.

Do not try to add argument names on tuple elements

Add user visible option to opt-into running IDE features OOP.

Move initialization earlier.

Creates a new package, Microsoft.NETCore.Compilers, which contains
CoreCLR-compatible versions of csc and vbc compiled against the
netcoreapp1.1 shared framework. This NuGet package can be referenced
by any C# or VB MSBuild project as long as the `dotnet` command line
tools and the netcoreapp1.1 framework is installed.

Add the remote endpoint for Add-Import and hook up to VS.

Rename experiment to fix 16 char requirement.

Use json serialization for some of our OOP types to simplify things.

Add option to control running Add-Using out of proc or not.

Break types into their own files.