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

[Michael Buch via cfe-commits]

Michael137 wrote:

> What is debug info size impact?

Realistically this will add a few more abbreviations into `.debug_abbrev` and only a few extra bytes per-UBSAN trap (abbreviation code + 1 ULEB128 for the index into the string offset table) into `.debug_info`. The rest of the `DW_TAG_subprogram` is encoded in the abbreviation for that fake frame. But I don't have a good intuition for how many UBSAN traps get emitted for a large codebase. So @anthonyhatran try this on a bootstrapped Clang build

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