Scripts/BloodFurnace:
* cleanup InstanceScript
* fix broggok poison cloud

Scripts/Naxxramas/Grobbulus:
* fix poison cloud
* fix mutating injection
Fix build
DB/Spawns: remove duplicate NPCs on Zeppelin from Orgrimmar to Thunder Bluff

Closes #11420
Core/SAI: drop unneeded code
Scripts/PoS/Garfrost: cleanup saronit blocks after death
Core/Battlefield: some codestyle changes
Core/Spells: Fix potions cooldown in combat

Fix a cooldown issue related to potions allowing Players in combat to use more than 1 potion in a row, especially with high latency.
This also fixes an exploit about using infinite potions in combat just by skipping the client-side check.
The original implementation c064c2e2e1eebd43b273365583dd181293bafa22 was missing a check in Spell::CheckCast() about this particular case since Potion cooldown is added only after the Player goes out of combat.
Fixes #1259 .