[clang] [clang][python] Add CLANG_DISABLE_RUN_PYTHON_TESTS CMake option to disable clang python bindings tests (PR #111367)

[Alex Bradbury via cfe-commits]

asb wrote:

> > We already have hard-coded logic to disable adding these tests to the `check-all` target in various cases.
> 
> Why do you have to do that?

I've never worked with the clang python bindings before, but you can basically see the reasoning in https://github.com/llvm/llvm-project/blob/bf7022f71a95313e8ebdd34e5ea7cb7bca90a24d/clang/bindings/python/tests/CMakeLists.txt - there are various targets and configurations where they are expected or known to fail.

https://github.com/llvm/llvm-project/pull/111367