[clang] [Clang][CodeGen] Add metadata for load from reference (PR #98746)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

So for ubsan, we have checks when you construct a reference, and you think that's sufficient?  I guess that's probably fine. At least, I don't think we need to revisit that decision here.  (I suspect it might make sense to check references that come from arbitrary memory, but that's really a separate discussion.)

https://github.com/llvm/llvm-project/pull/98746