[WFLY-2512] Simplify registration of chained transformers for subsystems

Fixes for https://github.com/wildfly/wildfly-core/pull/39/files#r15152121.

I have left making the definitions of the chains explicit, I don't like auto-generating/guessing those since:
* In long chains sometimes a version is empty and gets added automatically. e.g. if you have 1.4->1.3->1.2->1.1, and there is only a transformer for 1.4->1.3, we don't explicitly need to create builders for 1.3->1.2 and 1.2->1.1. This is done by the build(ModelVersion...versions) method and driven by the versions passed in.
* In some cases, such as the core transformers, the chains are totally different (EAP 6/AS7 is current->1.6->1.5->1.4->1.3->1.2, while WF 8+ is current->2.1->2.2)