Feature/create core test package

[essweine]

This is basically pre-work for fixing up the execution model. I've

• removed python2 mutex support and some related attributes (I guess -- they might have done something sometime, but they definitely don't have any effect now)
• reorganized some of the task.py code so that related methods are near each other, making everything easier to understand
• replaced PatternTest and the serializer test that inherited from it with a base class containing the tests and subclassed tests for each pattern. I am really sick of:
  • seeing that PatternTestfailed
  • editing the test to print out the workflows that no longer work to get an idea of what I'm up against instead of failing on the first one
  • then editing the test to run only each failing workflow at a time

I hope I've also fixed the problems with the CI job requiring a bunch of sys.path inserts to run the tests. I don't need them locally, but going to mark this as a draft until I figure out whether that works.

[essweine]

Apparently the CI job still won't work, and I can't change it (or possibly don't know how, but there is no way to do so that's obvious to me). I run tests from the top directory with
python -m unittest discover -v -s .-p *Test.py
which seems to me like a totally reasonable way to run the tests (as opposed tocding to tests/SpiffWorkflow and then running the tests, which is what the CI job does) so IMO this is a problem that needs to be fixed.
Maybe somebody else who has more interest in solving this problem can take it over.

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[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
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0.0% Coverage
0.0% Duplication

[essweine]

Turns out the tests with the failing imports were not to the new test, and also we were missing some schema files. Anyway, the tests pass now, no matter what directory they're run from. Sonarcloud thinks there's new code, but there really isn't anything new -- I just moved some things around so related methods were near each other, and removed some duplicated code.