(nixos/)knot-resolver: 4.3.0 -> 5.0.0

Minor incompatibilities due to moving to upstream defaults:
  - capabilities are used instead of systemd.socket units
  - the control socket moved:
    /run/kresd/control -> /run/knot-resolver/control/1
  - cacheDir moved and isn't configurable anymore
  - different user+group names, without static IDs

Thanks Mic92 for multiple ideas.