Item display as pet entites

[ErikSzabo]

Added config option to use item displays as pet entities,
It is way smoother, it doesn't have display name bugs, and way better for performance.
It also doesn't have any hitbox unlike the armor stands. Your current armor stand implementation blocks melee hits and projectiles if you hit the head of the armor stand.

Another small fix is the invisibility effect bug. Now the pet gets correctly removed when the player becomes invisible.

Bumped the API version to 1.20.4 (from 1.19.3) to have access to all item display APIs but it should properly work in older versions if the item displays are disabled in config (which is disabled by default).

[ErikSzabo]

teleportDuration on ItemDisplay is available from 1.20.2, meaning everyone above 1.20.2 could use the item displays for pets instead of armor stands.