resolved: imply SD_RESOLVED_NO_SEARCH when looking up trailing dot domains

resolved: imply SD_RESOLVED_NO_SEARCH when looking up trailing dot domains

Let's turn off the search domain logic if a trailing dot is specified
when looking up hostnames and RRs via the Varlink + D-Bus APIs (and thus
also when doing so via nss-resolve). (This doesn't affect lookups via
the stub, since for the any search path logic is done client side
anyway)

It might make sense to force the DNS protocol in this case too (and
disable LLMR + mDNS), but we'll leave that for a different PR — if it
even makes sense. It might also make sense to disable the logic of never
routing single-label lookups to the Internet if a trailing to is
specified, but this needs more discussion too.