Reduce extraneous testing files

[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

Add generated files to .gitignore

Previously we had been including files in tests/integration/generated in the git repo for zppy. This has a few issues:

• The developer has to remember to re-generate files to include in the PR if any changes are made to the underlying template cfg.
• Both the template cfg and the generated files end up in the PR, cluttering the PR for code reviewers.
• Generated files can only be made for the machine the developer is currently on. That means there is usually only generated files for Chrysalis and none for Perlmutter or Compy.

The original purpose of keeping the generated files outside .gitignore was that users could refer to them as examples. Now though we have several example cfgs:

• zppy/examples/post.*.cfg
• docs/source/post.*.cfg

Related request

We should probably consolidate example cfgs into just one of those directories.

Remove extraneous "min case" tests

The "min case" tests were originally designed to test smaller use cases. However, the latest versions of the test suite allow customization of which cfgs and which tasks run. That means we can likely remove many of the minimum case tests. Ones that actually test cases not covered by the comprehensive tests should remain.

Related request

It would be nice to automate testing of the remaining min-case tests as well -- i.e., include them as part of the standard test suite.