Add CI and nightly tests for regrid scripts

[mathomp4]

This is a "might be possible" thing.

First, add a suite of regrid.pl tests beyond the current single one done at night on discover.

Second, could we do a CI test of regrid.pl (and maybe regrid.py in future)? This requires a few things:

1. The docker image needs restarts. These are in the bcs variant
2. The docker image needs BCs. This is the harder one. I might have trimmed the BCs in TinyBCs of any unneeded cruft. So I might need some @bena-nasa (upperair) and @weiyuan-jiang (land) help finding all the necessary files. (Who knows, maybe they are all there?!)