Changes

`conversion_duration` property on Zombies and Zombie Villagers (#2302)

* `conversion_duration` property

* these tags aren't static

* deprecate `drowned_conversion_duration`

* seconds -> ticks

* prevent exceptions by checking if entity is converting

* remove redundant method

* exclude PigZombies

* remove redundant tags arr

* prevent exceptions in property string
(commit: 689ef23)