Hard-code default values in messaging-activemq subsystem.

The messaging-activemq subsystem defines plenty of attributes that maps to Artemis configuration.
Most of these attributes have default values. The default values are taken from Artemis API (ActiveMQClient., ActiveMQDefaultConfiguration.)

This has the advantages that we use the sensible default values provided by Artemis itself.
However there some unintended consequences. When Artemis change one of this default, it also changes the default value of the corresponding WildFly attribute. We have strict rule to handle this (with resource transformers, etc.) but this should not be something by happen by accident. We don't have a mechanism today that catch this kind of issue. Some of this may be caught by transformers tests if the resource is actually defined in the transformers configuration (but usually I only add a resource to the transformer when I am explicitly changing its definition).

We should hard-code all default values of the messaging-activemq subsystem instead of relying on Artemis API (the actual value will often be the same than the one provided by Artemis though).
This will protect us of Artemis API changes so that we can decide to change a default value when it makes sense separately of Artemis upgrades.
However, we will have to sync with Artemis when they do such changes to figure out if we should do that too or keep the previous value.