Villagers' equipped armor is deleted when converting to witches

Since it was requested that MC-311623 be split up, this report covers equipment transfer when a villager converts to a witch.

When such a conversion occurs, the villager’s equipment is deleted. Per the standard outlined in MC-311623, it would be expected that the items a witch cannot make use of (all equipment slots) would be dropped according to drop_chances (preferably reflecting the chance value exactly).

(Note that villagers being able to wear armor is intended per MC-555615, MC-261666 and related reports.)

To reproduce

1. /summon minecraft:villager ~ ~ ~ {NoAI:1b,equipment:{head:{id:chainmail_helmet}},drop_chances:{head:2f}}

2. /summon minecraft:lightning_bolt

3. /data get entity @n[type=minecraft:witch] equipment
   ❌ The helmet has been deleted

Expected behavior

The helmet would be dropped on the ground (utilizing invulnerable_time to avoid the lightning damage).