nixos/services.mysql: Fix restart on-abnormal (#430859)

- The `services.postgresql` module now sets up a systemd unit `postgresql.target`. Depending on `postgresql.target` guarantees that postgres is in read-write mode and initial/ensure scripts were executed. Depending on `postgresql.service` only guarantees a read-only connection.

- The `services.mysql` module now restarts the database `on-abnormal`, which means that it now will be restarted in certain situations, it wasn't before. For example an OOM-kill.

- The `services.siproxd` module has been removed as `siproxd` is unmaintained and broken with libosip 5.x.

- `services.tor.torsocks.enable` no longer defaults to true if Tor and Tor client functionality is enabled.

      serviceConfig = lib.mkMerge [

        {

          Type = if hasNotify then "notify" else "simple";

          Restart = "on-abort";

          Restart = "on-abnormal";

          RestartSec = "5s";

          # User and group