The earlier-recommended "pat1:pat2:pat3[x:y]" notation doesn't work well
with IPv6 addresses, so we recommend ',' as a separator instead. We know
that commas can't occur within a pattern, so we can just split on it.
We still have to accept the "foo:bar" notation because it's so commonly
used, but we issue a deprecation warning for it.
Fixes#12296Closes#12404Closes#12329