[pedrozc90]

Shows one icon for the shared potion cooldown, without listing potion item IDs.

Changes

• data.CreatePotionCooldown(enabled) adds one potion row to the shared gear cooldowns.
• The cooldown element scans the bags at load and on BAG_UPDATE_DELAYED. It maps each potion's use spell to its item ID. A potion is any item with class Consumable / subclass Potion.
• When a mapped spell is cast (UNIT_SPELLCAST_SUCCEEDED), the row switches to that item and reads its cooldown with C_Container.GetItemCooldown.
• Potions stay mapped after they leave the bags, so the last potion's running cooldown stays shown.
• The potion icon shows the item tooltip.
• /filger dump and tests/dump.lua label the potion row.

Tested

• MoP Classic:
  • The icon shows after drinking, with the correct timer.
  • The tooltip works.
  • Drinking the last potion keeps the icon.
  • A potion-class item with its own cooldown (86569) takes over the icon when used.
• make check and make test pass.

Not tested yet

• Era / TBC: whether SPELL_UPDATE_COOLDOWN fires on potion cooldowns. If it doesn't, these clients need BAG_UPDATE_COOLDOWN.
• Era: whether potions have item class 0 / subclass 1.
• Retail: whether healing and combat potions share a cooldown.
• MoP: drinking in combat.
• After /reload during a running potion cooldown, the icon only returns after the next drink.

Closes #7