Observer trigger fields rework

[Vrixyz]

• Trigger fields have been confusing to use, discussion on discord from https://discord.com/channels/691052431525675048/692572690833473578/1328735161474482216 suggested a new implementation:

current	proposed	comment
??? (when exposed through event (see pointer: trigger.event().target))	trigger.target	the thing that event was fired on
trigger.target	trigger.observed_on	the thing that the event was received on
trigger.observer	trigger.observed_by	the entity holding the observer state

I'd personally like to see a practical implications of that over recent work of #19245.

[hukasu]

Related (maybe)

• feat: allow for Trigger to provide the Entity on which an event w… #18710
• Distinguish .target() and .target in Trigger<Pointer<E>> #18982