[clang] [HLSL] Make it possible to assign an array from a cbuffer (PR #134174)

[Justin Bogner via cfe-commits]

https://github.com/bogner approved this pull request.

The fact that we get memcpy here points out some of the issues we have with representing cbuffers - it would really be nicer if this ended up generating elementwise copies instead. However, I think fixing that is out of the scope of this change (it'll also come up for structs, etc) and will be rather complicated, so this looks reasonable to me.

https://github.com/llvm/llvm-project/pull/134174