[BUG] OxygenXML not compatible yet with 'develop'

[dizzzz]

The oxygenXML editor is not yet compatible with 'develop'.

Two reasons

1. Java 21
   Oxygen is yet bundled with Java17; as develop is built with Java21, the eXist-db classes can't be loaded
   Work around: remove bundled OpenJDK from oxygen

2. xmldb-api change
   the API has been modernized and updated. as a result OxygenXML shows the following error:

Exception in thread "AWT-EventQueue-0" java.lang.NoSuchMethodError: 'java.lang.String org.xmldb.api.base.Resource.getResourceType()'
	at ro.sync.db.nxd.exist.k.getTooltip(Unknown Source)

this requires an update of the editor.

[raducoravu]

@dizzzz for (2) I made some changes in our code, Oxygen 28 which we plan to release in September will have a fix for this.
For (1) indeed Oxygen would need to be run with Java 21 and officially we do not support it. Or who knows, maybe we'll find the time to officially support Java 21 in Oxygen 28, we started some work on it, but I'm not sure about that.