packit: Move fmf metadata into upstream

packit: Move fmf metadata into upstream

This moves https://src.fedoraproject.org/tests/systemd into upstream
so it's one less moving piece that we need to remember. While we're at
it, do various cleanups as well:

- Remove non-packit logic
- Set NO_BUILD in mkosi.local.conf as it's not picked up from the
  process environment
- Don't set unused environment variables
- Remove workdir logic as we run in an ephemeral VM already
- Drop --verbose from meson test to reduce noise
  from passed tests
- Use mkosi sandbox and drop duplicated deps from metadata file
- Stop running the unit tests as they already run as part of the rpm
  build and as part of the integration tests.
- Various style fixes