This tmt[0] test runs the playwright tests as gating tests. Having the
gating tests upstream avoids duplication across fedora and centos
dist-git repositories, and running them upstream should keep them in
working order.
Only add x86_64 for now, the aarch runners seem to be a bit too slow.
[0]: https://tmt.readthedocs.io/en/stable/index.html
Makes the test's base url, user & password configurable through the
environment. Abstracts differences between hosted and cockpit where
possible to lib, and adds conditionals otherwise.
