Allays can get stuck and freeze inside non-full blocks

The bug

Allays can get stuck inside non-full blocks, such as fences.

Affected blocks

Slim blocks:

1. Bamboo
2. Chain
3. Door
4. End rod
5. Fence
6. Fence gate
7. Glass pane
8. Grindstone
9. Iron bars
10. Lightning rod
11. Pointed dripstone
12. Sea pickle
13. Stained glass pane
14. Wall

Other blocks:

1. Cauldron and composter (MC-251364)
2. Hoppers (MC-251648)
3. Slabs
4. Stairs

To reproduce

• Execute the following command:
  /fill ~20 ~-20 ~20 ~ ~ ~ minecraft:acacia_fence hollow
• Summon allays inside and outside the fence cube.

Expected result

The allays should be able to pathfind around the fences.

Observed result

The allays get stuck inside the fences.

Original description

Flying mobs can no longer move on their own when they wander into a non-full block, most commonly seen with fences (until the block is removed or the mob is pushed out by other means. This is assumedly what caused MC-250321, with the difference being that it doesn't crash the game.