[Offload] Add framework for math conformance tests on GPUs

[leandrolcampos]

This PR introduces the initial version of a C++ framework for the conformance testing of GPU math library functions, building upon the skeleton provided in #146391.

The main goal of this framework is to systematically measure the accuracy of math functions in the GPU libc, verifying correctness or at least conformance to standards like OpenCL via exhaustive or random accuracy tests.

[github-actions]

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[jhuber6]

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

[jhuber6]

Everything looks good, but we should handle the tests in a single binary rather than splitting them between platforms and providers. The test should simply execute dependent on what the user could compile. Like if they had an AMDGPU machine with HIP math it should detect that and use the proper platform and launch the extra kernel.

[github-actions]

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