[WFLY-3883] use a LIST for the JMS connection-factory's connector attribute

and for the pooled-connection-factory too.

* for legacy versions, the LIST of STRING is converted to a MAP by the
  messaging transformers
* the attribute defines a value converter to ensure than legacy
  operations (that uses a MAP) can still be executed on the latest
  version.

JIRA: https://issues.jboss.org/browse/WFLY-3883
That's already what the current code does in the master branch.

The attribute uses a `SimpleMapAttributeDefinition` (so it's an `OBJECT`) and it has a `ParameterCorrector` that converts a `LIST` (e.g. `["in-vm", "other"]`) to the expected object format `{"in-vm" => undefined, "other" => undefined}`)