Remove old IDocumentHIghlightsService.

Update breaking change doc for the #24806

Merge dev15.7.x to master

Simplify definite-assignment check for InlineDeclaration codefix

Doc change related to: https://github.com/dotnet/roslyn/issues/24806

Remove find refs window

Merge dev15.7.x to master

SubstituteNoPiaLocalType - use comparison of SpecialTypes to match bases across distinct core libraries. (#24965)

Grammar fix

Merge 15.6.x to 15.7.x

Merge dev15.6.x to dev15.7.x

Merge dev15.7.x to master

Revert "Enable multicore JIT in the compilers (#23173)"

* Include PDB Checksum in Debug Directory

* Xlf files

* Add more validation

* Fix tests

* Fix xplat test

* Remove data signature

We've seen crashes that appear to be involved with multicore JIT that
only started soon after multicore JIT was enabled for the compiler
(tracked in #23846). This change disables multicore JIT until we can fix
the root cause of the crashes.

Merge dev15.7.x to master

* Permit selecting an instance from a type in a sub-expression in nameof(...)

Fixes #20600

Ignore elastic trivia when formatting single line local functions, so they stay single line local functions.

Skipping PasteCommandWithOutInteractiveFormat test