main/clang: upgrade to 14.0.4

This adds main/llvm14 and updates main/clang to 14.0.4

Note: llvm14 depends on testing/py3-recommonmark for generation of the documentation. If I understand correctly, main packages may not depend on non-main packages, even if this is a build time only dependency. However, just moving testing/py3-recommonmark to main is not enough, as it in turns has dependencies outside of main, which have dependencies outside of main, which have dependencies outside of main, etc. If we don't want to end up moving half of the python packages to main, we either need to disable the documentation or allow buildtime only deps outside of main