Automatic tests missing for external/combined rotations

In terms of rotations/orientations, the current CI pipeline only tests head rotations. !540 (merged) introduced also external orientations to the codec. These two orientations (head + ext) are combined into a single orientation in the codec. The external orientations should also be tested in the CI pipeline, with all its variations (enable/disable/freeze flags + orientation interpolation) that were made available in the contribution.