Intrinsics analyzer and fixes (#85481)

Intrinsics analyzer and fixes (#85481)

* Implement analyzer for platform intrinsics use in System.Private.CoreLib

This analyzer detects the use of all platform intrinsics and checks to
ensure that they are all used either protected by an if statement OR
ternary operator which checks an appropriate IsSupported flag, or that
the intrinsic is used within a method where the behavior of platform
support for the intrinsic is not allowed to vary between compile time
and runtime. The analyzer attempts to be conservative about allowed patterns.

All existing code in System.Private.CoreLib has been annotated to avoid producing
errors.

See the markdown document for details.

Co-authored-by: Jeremy Koritzinsky <jkoritzinsky@gmail.com>