Mixing Hibernate and a JTA provider may lead to duplicate JTA
dependencies as the API is published with different coordinates.

The following has been applied:

* We now use `javax.transaction:javax.transaction-api` everywhere.
* The `data-jpa` starter has been updated to replace the JBoss JTA
  dependency with the standard one.
* The `jta-bitronix` starter has been updated to use JTA 1.2 instead of
  JTA 1.1 (unfortunately, JTA 1.1 is published with different
  coordinates).
* The `jta-atomikos` starter has been updated to define a dependency on
  JTA as the current version does not do it at all.
* The HornetQ JMS server is also relying on JTA but that dependency
  should have been optional. It has been excluded for the time being as
  it was using (yet) another set of coordinates.

Fixes gh-2092