pydantic in place of _Makers

[anschweitzer]

This branch show's an example of significantly reduced cacs.

• Enum symbolization removed (for visualization purposes; experimenting adding that in next)
• Cac data classes are unused. I couldn't find a case where they were any different than the CacGt versions; we can add them if we want.

It's ok if we don't merge this branch. It's purpose is comprehension of ideas for both of us.

Changes are:

• Removed comments / doc from field definition, for short term visibility
• Cacs inherit from ComponentAttributeClassGt and only add new/changed fields.
• HardwareLayout uses ComponentAttributeClassGt not ComponentAttributeClass.
• load_cacs() is simpler.
• All cacs loaded through CacDecoder, which by defaults gets its list of supported cacs from gwproto.types.cacs.
• Includes suggested 'default value' changes.
• Uses UUIDStr to get UUID validation on id strings via a type name.
• Logging removed from gt classes as it is a source of warnings.
• Existing test code reduced to taking the existing dictionary and verifying calling load_cacs() on it loads the expected type of cac. (Enum symbolization commented out; to be added next).
• Updated cacs:
  • ComonentAttributeClassGt
  • ElectricMeterCacGt
  • MultipurposeSensorCacGt
  • PipeFlowSensorCacGt
  • RelayCacGt
  • ResistiveHeaterCacGt
  • SimpleTempSensorCacGt