checks: mon: should listen on public interface/ip

It is possible to configure this incorrectly and make a monitor listen on the private/cluster interface, which will cause monitors to never form quorum

The issue names no files, tests, or entry points. Start by locating the monitor configuration check and tracing how its listening interface or IP is selected; done means a monitor cannot be configured on the private or cluster interface and quorum behavior is covered by a regression test.

Written by the indexing model from the issue text.