Add tests for older cfgs

[forsyth2]

Request criteria

• I searched the zppy GitHub Discussions to find a similar question and didn't find it.
• I searched the zppy documentation.
• This issue does not match the other templates (i.e., it is not a bug report, documentation request, feature request, or a question.)

Issue description

Currently, zppy's test cfg files get updated as parameters change. We need some way to test that older cfgs still work. This would cover cases like:

• Is that new parameter in main required, or can it be safely ignored?
• Does that deprecated parameter in this old cfg give a warning/error?

[forsyth2]

I think the simplest way to implement this would be to include the "official" comprehensive test cfg files and expected results for each release. That is, at every zppy release, we make copies of the current comprehensive test cfg files and freeze them as "test_zppy_v#.#.#.cfg, while making active updates to the original cfg files.

[forsyth2]

This was accomplished with #720, closing.