java: simplify the CommonListener stuff

by moving the MethodInvocation to be purely an internal detail

Change-Id: Id7863261abd5ebd30b7596bac756ca5360119283
Reviewed-on: https://gerrit.libreoffice.org/13100
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>