Rework localized tox scripts

Use tools/test-languages.sh as common script for all three tox jobs and
parametrize it accordingly.

This refactoring simplifies the setup and removes some duplication.

Remove now obsolete file tools/copy_pom.

Change-Id: I5590e836621fe58f761675132bdd71e3f1254174
Merge "Rework localized tox scripts"