Simple mobs movement while resting

[MarsM0nd]

Issue Description:

When a simple mob rests, buckles to a chair, and unbuckles, they can move even though they are still resting, and their rest should stop movement.

What did you expect to happen:

For them to be in either state, not resting and able to move, or resting and not able to move

What happened instead:

Didn't have movement blocked, even though the rest of the effects of laying down applied

Why is this bad/What are the consequences:

Inconsistent behaviour

Steps to reproduce the problem:

Spawn in as simple mob, rest on a chair, buckle in, unbuckle, move

When did the problem start happening:

Probably since #17899, as humans can move while laying down, so unbuckling from a chair while still resting doesn't re-add the immobilized trait

Extra information:

Mob gets uiblocked, pullblocked, and immobilized while resting (lying_down as reason for the traits in the list), only immobilized while buckled in the resting state (only reason in the list is buckled), only uiblocked and pullblocked after unbuckling (lying_down as the reason for them).