[clang] [OpenACC][CIR] Implement beginning of 'copy' lowering for compute con… (PR #140304)

[Bruno Cardoso Lopes via cfe-commits]

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

> @bcardosolopes : If it is alright, I'd like to just do the OpenACC clause refactor in a followup patch. I'll work on it 'next', immediately after this one. I'd originally done the visitor, then realized it needed to be accessed from 3 places.

Sure thing!

https://github.com/llvm/llvm-project/pull/140304