Allow users to exclude subsystems from metrics scanning

In the various subsystem that have a 'exposed-subsystems' attribute like https://docs.wildfly.org/27/wildscribe/subsystem/metrics/index.html, work out a mechanism to expose all but a list of excluded ones.

For example, excluding metrics from the messaging-activemq subsystem would be a potential workaround for the problem discussed at https://groups.google.com/g/wildfly/c/UOmzxLoL4gQ.