[llvm] [Offload] Introduce offload-tblgen and initial new API implementation (PR #108413)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

Generally I'm in favor of `ol_` as a prefix, `snake_case` for the C API, and `get_x` as the verbage.

https://github.com/llvm/llvm-project/pull/108413