[Feature] Add support for -1 extradmgskill to allow all skills to be scaled. (#3136)

* [Feature] Add support for -1 extradmgskill to allow all skills to be scaled.

- `$mob->GetSkillDmgAmt(skill_id)` now uses `int` instead of `uint16`.

- `statbonuses:GetSkillDamageAmount(skill_id)` now uses `-1` properly.
- `mob:GetSkillDmgAmt(skill_id)` now uses `int` instead of `uint16`.

- A `-1` value in `extradmgskill` denotes the ability to scale all skills at once.
- Consolidated `AddItemBonuses()`, `AdditiveWornBonuses()`, `CalcItemBonuses()`, and `CalcRecommendedLevelBonus()` to mob-based methods to avoid code duplication.
- Bots, NPCs, and Mercs can now use additive worn effects if the rule is enabled, as well as all other proper stat bonuses that only clients had before.
- No SQL update required to change `extradmgskill` and `extradmgamt` to `int` as they already are this type in the database, just had to adjust `item_data.h` and `shareddb.cpp`.

* Update mob.cpp

* Cleanup.

* Cleanup.

* Move #include <vector> to header.

* Add method for GetExtraDamageSkills

* fix additembonuses

* Update bonuses.cpp

* Update mob.cpp

* Out of bounds.

* Update bonuses.cpp

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Co-authored-by: Aeadoin <109764533+Aeadoin@users.noreply.github.com>

zone/merc.h

@@ -268,10 +268,6 @@ public:
 	bool FindTarget();
 
 protected:
-	void CalcItemBonuses(StatBonuses* newbon);
-	void AddItemBonuses(const EQ::ItemData *item, StatBonuses* newbon);
-	int CalcRecommendedLevelBonus(uint8 level, uint8 reclevel, int basestat);
-
 	int64 GetFocusEffect(focusType type, uint16 spell_id, bool from_buff_tic = false);
 
 	std::vector<MercSpell> merc_spells;