Refactor machine ownership to use player uuid

[omergunr100]

What

Stores placer uuid instead of ownership object.
Ownership objects still exist but are generated in the getter.

Outcome

This should solve some edge cases in our current implementation:

1. machines would cache teams that no longer exist.
2. when a player leaves the team the machine ownership object would keep both the team and player even though one should be invalid. (in this implementations machines belong to the player first and team second)

Potential Compatibility Issues

Will remove all machine ownership data from existing worlds.
Moved ownership from block entity to meta machine so...
Any addon that re-assigned ownership will need to change from machine owner object to player uuid.

[krossgg]

One further thought - maybe you could create a static UUID->IMachineOwner cache so that you don't have to create new instances of owners every time you call a get. Doesn't need to be persisted to savedata or anything.

[omergunr100]

tbh ownership should be moved from the block entity to the machine since the block entity holder can't be synced and there's no reason for the owner field to randomly just sit there.

[krossgg]

Another note, are the IMachineOwner methods save, load, and create (+ impls) still necessary? Seems that the owner itself is no longer serialized unless I missed something.