Canreach refactor (#93165)

## About The Pull Request
ports https://github.com/DaedalusDock/daedalusdock/pull/1144
ports https://github.com/DaedalusDock/daedalusdock/pull/1147

full credit to @Kapu1178 for the juice

instead of `reacher.CanReach(target)` we now do
`target.CanBeReachedBy(reacher)`, this allows us to give special
behavior to atoms which we want to reach, which is exactly what I need
for a feature I'm working on.
## Why It's Good For The Game
allows us to be more flexible with reachability
## Changelog
🆑
refactor: refactored how reaching items works, report any oddities with
being unable to reach something you should be able to!
/🆑

code/datums/ai/basic_mobs/basic_subtrees/attack_adjacent_target.dm

@@ -26,7 +26,8 @@
 
 /datum/ai_behavior/basic_melee_attack/opportunistic/perform(seconds_per_tick, datum/ai_controller/controller, target_key, targeting_strategy_key, hiding_location_key)
 	var/atom/movable/atom_pawn = controller.pawn
-	if(!atom_pawn.CanReach(controller.blackboard[target_key]))
+	var/atom/atom_target = controller.blackboard[target_key]
+	if(!atom_target.IsReachableBy(atom_pawn))
 		return AI_BEHAVIOR_INSTANT | AI_BEHAVIOR_SUCCEEDED
 	. = ..()
 	return AI_BEHAVIOR_DELAY | AI_BEHAVIOR_SUCCEEDED

code/datums/ai/basic_mobs/basic_subtrees/escape_captivity.dm

@@ -60,7 +60,7 @@
 	if (QDELETED(target))
 		return FALSE
 	var/mob/living/pawn = controller.pawn
-	if (!pawn.CanReach(target))
+	if (!target.IsReachableBy(pawn))
 		return FALSE
 	return pawn.loc == target || pawn.buckled == target