Rename battle anim type files, remove unneeded ARG_RET_IDs

include/constants/battle_anim.h

@@ -392,7 +392,7 @@
 #define B_ANIM_STATUS_NIGHTMARE         0x8
 #define B_ANIM_STATUS_WRAPPED           0x9 // does not actually exist
 
-// Most tasks return a value to gBattleAnimArgs[7].
+// Tasks with return values often assign them to gBattleAnimArgs[7].
 #define ARG_RET_ID 7
 
 // Trapping Wrap-like moves end turn animation.