Cross-image testing

[kurtkilpela]

All RSR testing occurs within a single image. I believe this has the potential to hide defects that cross-image testing would show.

One example, the main-v2 branch supports v1 and v2 of the wire protocol. While the v1 protocol implemented in this branch is self-consistent, no automated testing shows that it is consistent with the implementation in the main-v1 branch. Cross-image testing would confirm compatibility between the branches.