Merge dev15-preview-5 into master

Support tuple element names in locals and expressions in the EE

Merge microupdate into master

Adds a new refactoring that offers to convert existing null-check+throw code to use ?? + throw-expr.

* Implement new syntactic disambiguation rule for pattern-matching
* Distinguish 'is' from 'as' when parsing the type
* Refactor type parsing modes to an enum.

Fixes #10492
Related to #13813

Roslyn uses the CLR APIs to sign an assembly, so as long as the CLR
supports the key length and it is a valid key structure there's no
reason we should limit the length of the key. In addition, the previous
limit was wrong -- it didn't include padding space for the key header.

Fixes #12822

Avoid a null value key in the decision tree in error recovery situations.

Ensure that we call out to third parties in FAR in the same context that we were called on.

Fixes 7 failing pattern matching tests due to an incorrect assumption about standard cultural settings

Requires emitting tuple element names for locals to the PDB as custom debug information, similar to support for 'dynamic' in C# for the EE.

Make tests massively simpler.

Fix for "Some tests fail due to non-standard cultural settings" (#10362)

Remove code that doesn’t have any observable side-effects.

Adjust heuristic to choose a set of best candidates for overload resolution failure.

Properly handle null paths being passed to the RemotePersistenceService.

fix unit test failure due to pending workspace events

Metadata export for tuple element names in VB

This is the same fix as was implemented for C# in #13806, but for VB.

* fill out the visitor for BoundMethodGroup

* add vb tests and yield in c# test