[clang] [clang][Sema] Track trivial-relocatability as a type trait (PR #84621)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

Based on the poll results from Tokyo, P2786 is the direction EWG has taken for this functionality, so we should be focusing our efforts on supporting that direction. If WG21 changes direction again, we can shift again, (this builtin exists to support the standard's type trait and thus is experimental until the standard makes a final decision). I don't think we should put efforts into supporting a P1144-based approach.

https://github.com/llvm/llvm-project/pull/84621