List modules which contributed dependency conflicting with root

[Silic0nS0ldier]

With --check_direct_dependencies=warning|error the reason for errors is not given, complicating investigation.

This PR adds logic to find the "source modules" that brought the resolved version into the graph.

# BEFORE
ERROR: For repository 'rules_proto', the root module requires module version [email protected], but got [email protected]
in the resolved dependency graph. ...
# AFTER
ERROR: For repository 'rules_proto', the root module requires module version [email protected], but got [email protected]
in the resolved dependency graph. Source module(s): [email protected] ...

This same information can be retrieved with bazel mod commands, however this relies on;

• MODULE.bazel.lock existing
• MODULE.bazel.lock being in sync with MODULE.bazel

Neither of which is necessarily true when the check direct deps error/warning is shown.

If nothing else, this saves time.