[llvm] Reland #118503: [Offload] Introduce offload-tblgen and initial new API implementation (PR #118614)

[Jan Patrick Lehr via llvm-commits]

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

I ran this through different build configs and they worked fine. Let's give it another try, I guess.

https://github.com/llvm/llvm-project/pull/118614