[clang] [clang] Add value_type attr, use it to add noalias when pass-by-value. (PR #95004)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Also, we probably want to specify the interaction between trivial_abi and value_type here... should trivial_abi imply value_type?

https://github.com/llvm/llvm-project/pull/95004