Support basu as a sd_bus_provider

[TimB87]

Hello all :wave:

Is your feature request related to a problem? Please describe.

You don't seem to be able to run gamemode on non systemd/elogind distros.

Describe the solution you'd like

Maybe basu can bridge that gap for these distros: https://git.sr.ht/~emersion/basu

Describe alternatives you've considered

Additional context