core: do not disconnect from bus when failed to install signal match (#35779)

core: do not disconnect from bus when failed to install signal match (#35779)

If bus_add_match_full() is called without install callback and we failed
to install the signal match e.g. by timeout, then add_match_callback()
will disconnect from the bus. Let's use a custom install handler and
handle failures gracefully.

This does not *solve* the root cause of issue
https://github.com/systemd/systemd/issues/30573, but should improve the
situation when the issue is triggered.