run-tests: introduce a --pyoxidized option This options make it possible to use the pyoxidizer version to run the tests. This is a first basic version that is windows only. The test needs a working python, with Mercurial installed. However the pyoxidizer product is "self contains" without a "usable" Python. There have been discussion to have a fully functional `hg admin::python` command providing a fully functional python interpreter, but nothing is of the sort is ready yet. In In the meantime we use an hybrid approach, similar to what we do for testing `rhg`. We install a full "normal" Mercurial, but also the pyxodizer product as the official `hg binary`. That way, we use the pyoxidizer version or everything, but test that needs to run python have it available, with a fully functional Mercurial package. This first version is pretty basic (Windows only, no --local, not --with-pyoxidized), but it runs, various bug that we will have to fix. Differential Revision: https://phab.mercurial-scm.org/D11277