CAMEL-4407 has caused a regression in the features.xml

The scriptengine things that were added as part of CAMEL-4407 have made doing a features:install camel-script in a "plain" Karaf instance not work as those dependencies are not available in Central. Thus, setups that worked in the past that did not need those no longer work.

Propose moving those three deps to a "camel-script-optional" feature that would not be pulled in by default. If a user needs them, they would need to configure Karaf to pull from another repo.