Create activemq-client-javax module

[mattrpav]

This is the inverse of the activemq-client-jakarta. This will repackage classes under javax.jms.* namespace for the v6.x+ series to provide a backwards compatible client for use in legacy javax.jms.* JEE applications.

Where we can without too much pain to support back-ports, I'll see about dropping the JDK min to 11 to provide a wider range of backward compatibility as well.

[cshannon]

This should be put on hold for now, there is disagreement on the dev list about the need for this.