[llvm] [Offload] Add framework for math conformance tests (PR #149242)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

Some things to address:
Small LLVM style nits (header, braces, pragma once)
Detect user's platform based on input images (AMDGPU / NVPTX)
Re-use as much as possible of the LLVM libc utils (fpbits)
Don't worry about asynchronous launches for now

https://github.com/llvm/llvm-project/pull/149242