[clang] [Clang][CodeGen] Emit “trap reasons” on UBSan traps (PR #145967)

[Florian Mayer via cfe-commits]

fmayer wrote:

I would prefer this to be behind a flag (not necessarily in this PR), even if it's default turned on. People might not want synthetic frames added to their debug information and the top frame to point to the real code; also as this somewhat overlaps with the logic of `-fsanitize-annotate-debug-info`, with a flag people can choose which one they want.

https://github.com/llvm/llvm-project/pull/145967