Subsystem test framework tweaks

Instead of having all the .dmr files stored in the org.jboss.as.subsystem.test package in subsystem-test/framework, have the subsystems generate them on demand as needed. The generation is only done once per test run, and should also allow people to store the .dmr in the test resources using the same package as the test (the main reason for that is that I think there were some very rare cases where we needed to touch up the resource definition although that is probably for pre-resourcedefinition, i.e. 7.1.x).

This also reinstates the susbsystem test controller for 7.1.x transformers testing. These tests do not get run unless you specify -Djboss.test.transformers.subsystem.old. My thinking behind this is that when converting some subsystems to use chained transformers, I would rather do that for 'everything' to get as much coverage/corner cases as possible while this is fresh in my mind rather than in two versions time.

The subsystem tests for wildfly pass with this change.
This looks fragile...