Ensure that zenpacklib exports YAML as expected (ZPS-1746)

[j053ph4]

• Fixes ZPS-1746
• Updated EventClassSpec and ProcessClassOrganizer spec create/instantiate methods to return organizers
• Added missing 'replaceRegex' attribute to ProcessClassSpecParams
• Moved zenpack dumping methods to YAMLExport class mixin, where they can be unit tested without calling ZenScriptBase or the command line
• Updated ZPLCommand to use YAMLExport methods for dumping
• Added test_yaml_export.py unit test

[cluther]

I’m not sure why ZPS-1746 is even a problem. I thought we had decided that objects added by zenpacklib from YAML wouldn’t be exported. The only process classes that should be exported by zenpacklib --dump-process-classes are those that were loaded from XML, or created by the user and associated with a ZenPack.

This is related to ZPS-1601, and subsequent ZPS-2660 that had to fix the regression its fix caused.

There’s no need to export YAML for something when you can just find the YAML in the source file already.

I think the test case for ZPS-1746 is wrong. We should be testing by manually creating the process class through the UI, adding it to the ZenPack, then using zenpacklib --dump-process-classes to see if it dumps to YAML.