Introduce a new XML testing group

[zhfeng]

It is generally better to test with as little dependencies as possible, so that it does not happen that an extension that is there just for testing some niche feature brings some build steps that become vital for the execution of some basic functionality.

The grouping is given by the required dependencies. I.e. if the bean: test protocol requires an additional camel-quarkus-bean dependency, then it should be a separate test module with that dependency under the new group.

This need to follow up #4018