Fix issue preventing introduce-variable working on an expression being indexed into

Find-Refs on an accessor should only produce results for that accessor.

Merge dev15.9.x to master

Add GetCorrespondingLoop() (and Switch) branch operation extensions

Migrate to Microsoft.VisualStudio.Threading

There's a problem on MacOS where the pipe name may be too long to
use as a Unix domain socket. Unfortunately, there's no way in the
version of CoreFX that we reference to override the path name
used for the named pipe. If the path is too long then the compiler
server spins infinitely trying to connect to a path.

Since we can't use our own path, the best we can do right now is
abort compiler server usage if the path would be too long. This
commit adds a check on Unix machines running on CoreCLR to
detect when the constructed path will be too long, and bail out
if this is the case.

Use Concord API to get SymReader for EnC instead of IENCSymbolReaderProvider.GetSymbolReader. (#29177)

Add messages to NamedTypeSymbol.Construct exceptions

Bump 15.9.x to -beta2 version

branchOperation -> operation as API Design Team suggested

GetCorrespondingLoop and GetCorrespondingSwitch have been merged into a single
extension method.

Yet to come - 1. delete spurious extension methods, 2. rework unit tests.

Add support for colorizing escape sequences in string literals.

* Do not override assembly version in non-official builds

The toolset sets the assembly version to 42.42.42.42 if not set explicitly.

* Fix property name

* Fix build of the day number

* Set OfficialBuildId