AngryAt cannot be manually applied to endermen

The bug

An enderman cannot have their AngryAt modified with commands; this will result in the tag being removed and their AngerTime set to 0.

I'm aware modifying NBT of living entities is not supported, but when MC-188497 is fixed, this becomes an issue with setting it on-summon. I've opened a separate ticket for it because it is a separate issue.

How to reproduce

1. Try running this

   /data modify entity @e[type=enderman,limit=1,sort=nearest] AngryAt set from entity @e[sort=nearest,limit=1] UUID
   

2. Run /data get
   → The AngryAt tag is not present and AngerTime is set to 0