Entities don't interact with the world far from the player

It appears as though entities do not react to the world when far enough from the player, about 216 blocks. This includes:

Falling
Taking Damage
Aging (for entities with ticking NBT tags)

To reproduce:

1. Create a new superflat world with no entities
2. Run /summon chicken ~ 300 ~ {Tags:["MC-144678"]}
3. Run /data get entity @e[type=chicken,limit=1,tag=MC-144678] Pos[1] repeatedly

In 19w07a and before, this would return a slowly decreasing y value, which reflects the chicken falling. However, from 19w08a, the y value is stuck at 300.

Running /summon chicken ~ -300 ~ demonstrates how the chicken will not take damage if it is summoned in the void.

Of course, chickens are used because of their slow falling speed, which makes them easy to test. However, this will work with any entity. In particular, using items or area effect clouds means that their Duration or Age, respectively, does not update.