Closes#4504
Messages are not typical responses, so they need special handling. This
is different between RESP2 and 3, so this is the first instance where
the script layer needs to tell the difference.
- Recomputes checksums for pcaps to keep clean
- Removes some tests that had big pcaps or weren't necessary
- Cleans up scripting names and minor points
- Comments out Spicy code that causes a build failure now with a TODO to
uncomment it
