[clang] [CIR] Add offload container Op (PR #206576)

[David Rivera via cfe-commits]

RiverDave wrote:

For reference, in our staging fork, please refer to the pass implementation of DKE where we put this pass in use:
https://github.com/RiverDave/llvm-project/pull/12

https://github.com/llvm/llvm-project/pull/206576