[REALMS-9078] Realms freeze, disconnect everyone, and not saving when everyone leaves.

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Please also see this comment and this comment from Mojang.

Steps to reproduce
Create or join a realm.
Do anything.
Notice that mobs will start to freeze, containers and inventory won't open
Make sure everyone leaves, or wait for everyone to just be disconnected.
Join back.

Expected Results
You resume what you were doing.

Observed Results
The realm resets to what it was when you first joined.

Notes
According to this comment, template worlds locked at 1.17.11 do not have this issue when uploaded to a realm. The identical template world without the version lock does have these issues.