Projectiles which use item models use the "ground" display type and cannot be independently customized from it

The bug

Projectiles which reference item models (e.g. fire charges, eggs, snowballs, ender pearls, ghast fireballs, firework rockets, eye-of-enders) will use the "ground" display type, which is unintuitive since contact with the ground destroys most projectiles. It also forbids beinbg able to customize them independently of that item form when dropped on the ground.

How to reproduce

A resource pack is attached to this ticket.

1. Download and apply the attached resource pack

2. /give @s minecraft:egg[minecraft:item_model="minecraft:basalt"]

3. Drop this on the ground
4. Pick it up and throw it

Expected results

It would appear huge when dropped on the ground, but not when thrown.

Actual results

It appears huge when dropped on the ground and when thrown.

How to fix

Could be fixed by adding a new "projectile" display type, which would default to the standard "ground" display type if left unspecified (like what is done for the left hand display types), but could be customized independently.