[clang] [CIR] Copy byval records as bytes in CallConvLowering (PR #227170)

[Adam Smith via cfe-commits]

adams381 wrote:

@bcardosolopes this overlaps #224672, which fixes the same two sites (the callee spill and the call-site byval temporary).  Andy approved it yesterday.  It's only waiting on the `sve/len.c` breakage from #226534.  #224672 also passes the caller's storage directly when nothing writes it before the call, and copies from address-space-qualified sources, where this one falls back to the store.

https://github.com/llvm/llvm-project/pull/227170