Update systemd-oomd defaults to friendlier values
    
    - Remove swap policy. Default amount of swap (8GB?) is a lot lower than
      what we use internally with the swap policy. Which frequently leads to
      GNOME getting killed
      (e.g. https://bugzilla.redhat.com/show_bug.cgi?id=1941170, and other
      BZs not linked here). Internally we use 0.5x-1x size of physical memory
      for swap via swapfiles (this will be documented in systemd upstream).
      In simple cases of using more memory than is available (but without
      memory pressure), the Kernel OOM killer can handle killing the
      offending process.
    
    - Expand the memory pressure policy to system.slice, user-.slice, and
      all user owned slices. Support for ManagedOOM*= on user services was
      added in https://github.com/systemd/systemd/pull/20690 which allows
      us to be more fine grained on the pressure monitoring at the user
      level. In addition to the system.slice and user-.slice PSI monitoring
      this should result in a better systemd-oomd experience for desktop
      systems.