[clang] [llvm] [Offload] Move HIP and CUDA to new driver by default (PR #84420)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

> @yxsamliu Do you know what the next steps for merging this would be? I'd like to get it into the Clang 20 release if possible. The only thing this loses currently is managed variables being registered in RDC mode, but I'm going to assume that's hardly seen in practice so I could probably punt that until later. I unfortunately haven't figured out a way to reproduce the build failures on rocBLAS that the fork saw. I think @saiislam was looking into that but couldn't get docker to work.

I think at least we need to get this PR pass internal PSDB. We could discuss the docker issues internally.

https://github.com/llvm/llvm-project/pull/84420