Fix SPELL_AURA_MOD_AOE_AVOIDANCE

There is not a single spell using this aura, but now it works :)
Merge pull request #11849 from Unholychick/master

Fix SPELL_AURA_MOD_AOE_AVOIDANCE
Core/Movement: Fix LoS issue of NPCs chasing targets

Add Line of Sight checks to WorldObject::GetNearPoint(), fixing to TargetedMovementGenerator not reaching a point with valid LoS to the target and MotionMaster::MoveKnockbackFrom() knocking creatures inside walls.
Remove unused code.