preset: enable homed sidecar services

preset: enable homed sidecar services

As described in https://github.com/systemd/systemd/issues/31235, the preset
state for systemd-homed-activate.service was unclear. On the one hand, we have
a preset with 'enable systemd-homed.service', and systemd-homed.service has
'Also=systemd-homed-activate.service systemd-homed-firstboot.service', so
'preset systemd-homed.service' would also enable those two services, but
'preset systemd-homed-activate.service' would disable it, because the presets
don't say it is enabled. It seems that this configuration is internally
inconsistent. As described in the issue, maybe systemctl should be smarter
here, or warn about such configs. Either way, let's make our config consistent.

Follow-up for d1f6e01e4743ae94740314eeb46a162112ef4599 and
3ccadbce3358ba1db7ce5fa3f8dd17c627ffd93b.