[Clang][Sema] Use VersionMap from SDKSettings for remapping tvOS and watchOS availability

This makes the mapping between iOS & tvOS/watchOS versions more accurate. For example, iOS 9.3 now gets correctly mapped into tvOS 9.2 and not tvOS 9.3.

Before this change, the incorrect mapping could cause excessive or missing warnings for code that specifies availability for iOS, but not for tvOS/watchOS.

rdar://81491680

Differential Revision: https://reviews.llvm.org/D116822