Pull request type

• Code changes (bugfix, features)
• Code maintenance (refactoring, formatting, tests)
• ReadMe, Docs and GitHub updates
• Other (please describe):

Checklist

• Tests for the changes have been added (if needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest --runslow) have passed locally

Current behavior

A lot of repeated code in the motors' plots classes

New behavior

_SolidMotorPlots, _HybridMotorPlots and _LiquidMotorPlots now inherit _MotorPlots

Breaking change

• Yes
• No

Additional information

There are a lot of repeated code in _SolidMotorPlots and _HybridMotorPlots I could not find a good solution for it. I tried using multiple inheritance in _HybridMotorPlots but it went south really fast

Also, this is really useful for Motor Draws #436