[MC-311623] Inconsistent equipment preservation when a mob converts to another mob which cannot normally hold or wear it

Mojang requested that each conversion be tracked in its own report, so said reports have been created and linked as related to this one, and this one has been resolved as Invalid.

It would be expected that when a mob has any equipment (obtained either through normal means or through commands) and is converted to another mob which cannot normally wear or use such equipment, that there would be a consistent rule regarding whether or not such equipment is retained, dropped on the ground or deleted. This is not the case:

Conversion	Repro steps	Observed behavior	Tracked in other report
Hoglin → Zoglin	`/summon minecraft:hoglin ~ ~ ~ {equipment:{head:{id:chainmail_helmet}},TimeInOverworld:290,drop_chances:{head:0f}}`	Equipment is retained
Mooshroom → Cow	`/summon minecraft:mooshroom ~ ~ ~ {equipment:{head:{id:chainmail_helmet}},drop_chances:{head:2f}}` Shear it	Equipment is deleted
Pig → Zombified Piglin (body, saddle)	`/summon minecraft:pig ~ ~ ~ {equipment:{head:{id:chainmail_helmet},saddle:{id:saddle}},NoAI:1b,drop_chances:{head:2f}}` `/summon minecraft:lightning_bolt`	Equipment is deleted	MC-304420 (armor and hand items could potentially be tracked in their own report)
Tadpole → Frog	`/summon minecraft:tadpole ~ ~ ~ {equipment:{head:{id:chainmail_helmet}},Age:23900,drop_chances:{head:2f}}` `/data get entity @n[type=frog] equipment`	Equipment is deleted
Villager → Witch	`/summon minecraft:villager ~ ~ ~ {equipment:{head:{id:chainmail_helmet}},NoAI:1b,drop_chances:{head:2f}}` `/summon minecraft:lightning_bolt` `/data get entity @n[type=minecraft:witch] equipment`	Equipment is deleted	Armor is tracked in MC-305199
Zombie Villager → Villager (hands, body, saddle)	`/summon minecraft:zombie_villager ~ ~ ~ {equipment:{mainhand:{id:iron_sword}},ConversionTime:20,drop_chances:{mainhand:2f}}`	Said equipment is dropped only if the corresponding `drop_chances` entry is greater than `1f`	Armor is tracked in MC-311524, which as of writing this needs to be updated; but this is a related issue, rather than a sub-case of this issue, since villagers are intended to be able to wear armor (see MC-55516)
All mob type conversions not mentioned above (body and saddle)	(Omitted)	The behavior for body and saddle items for the conversion is the same as it is with other equipment

Note

My preferred solution would be to take the following line. During a conversion, for each piece of equipment,

If the output mob can make use of it, it is retained
If the output mob cannot make use of it, it is dropped on the ground with a chance exactly matching the input mob’s corresponding drop_chances entry

Note that villagers and witches should not be considered to be able to “make use of” their main-hand items, as this slot is simply overwritten depending on the circumstances.