[7668] Cleanup In CreatureAI function descriptions and AttackStart/AttackedBy use.

* Use AI::AttackStart calls only in case explicit request creature attack from core or AI code "attack it if can".
  Like taunt, pet handler attack command.
* Use AI::AttackedBy for reaction at hostile action "do something at hostile action"
  Like non-dot damage, swing, negative spell landing, or fade fear/etc.
  And provided by default call AttackStart if no current target.

This fix some problems, like:
* Civilian will react propertly at attack by another creature (not pet or player).
* Will not cases (at least triggred by core) when attack target start run to attacker before any real hostile action apply.

src/shared/revision_nr.h

@@ -1,4 +1,4 @@
 #ifndef __REVISION_NR_H__
 #define __REVISION_NR_H__
- #define REVISION_NR "7667"
+ #define REVISION_NR "7668"
 #endif // __REVISION_NR_H__