Improve onCaughtFire blockstate extension & maybe add event

[MehVahdJukaar]

Currently that call is called BEFORE the block is set, either as a fire block or as air.
This works ok for tnt stuff since thats meant to disappear anyways.
For anything else that is supposed to change state when its broken by fire however its not sufficent as any leve.setBlock call in that method will get invalidated by the subsequent call that sets block to air.

Also an event for this would definitely be nice. Could be use for example to react to fire burnig blocks, creating arbitrary new blocks there instead (i for example have a use cases for that where fire turns blocks into ash)

Related codein FireBlock