[clang] [mlir] [CIR][OpenACC] Implement 'routine' lowering + seq clause (PR #170207)

[Erich Keane via cfe-commits]

erichkeane wrote:

I'm not going to fix that clang-format failure, clang-format wants me to re-format that entire file, which I very much should not be doing. Please disregard it :) 

https://github.com/llvm/llvm-project/pull/170207