Rename CollaborativeStrategy to HivemindStrategy

[SeanNaren]

What does this PR do?

After discussion with the hivemind team, we've decided to follow course with the naming conventions that we've given to all other strategies. I think this primarily reduces noise, and makes it clear what the user is actually enabling.

Does your PR introduce any breaking changes? If yes, please list them.

Class name change, however since this feature has not been released in any version yet, I think it's fine to make the hard change.

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cc @Borda @SeanNaren