Add tests for config

[ipwnponies]

I moved the config logic to a separate module and added tests.

Summary of changes, in addition to the overall goal above:

• made this an executable package (python -m mealpy reserve foo bar baz)
• Added check-requirements check, it checks there are no requirements missing or extra from requirements.txt
• pyfakefs for effectively mocking file IO from open, pathlib, os.path, etc. Allows for running tests without accidentally reading/writing real files (which I most certainly did by accident lol)
• pytest-antilru for busting lru_cache under test

[ipwnponies]

@edmundmok bump, would like this change before I dive deeper into #7, as it introduces pyfakefs, which will make it easier to test caching files to disk.

[edmundmok]

@ipwnponies Sorry, just looked at it, was out the entire day yesterday.

[ipwnponies]

No worries, I put too much useful infrastructure into this PR that is helpful for follow up work.