[Github][TestingTools] Add workflow to build llvm-testing-tools
Add a github workflow to build the package. This just adds manylinux239
support for x86. Eventually we want to set up Windows/MacOS/AArch64
Linux and trusted publishing to automatically push this out to PyPI, but
for now this should be sufficient for testing.
Reviewers: ldionne, Michael137
Pull Request: https://github.com/llvm/llvm-project/pull/188891
