[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

---------

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

zone/lua_mob.h

@@ -392,7 +392,7 @@ public:
 	int GetModSkillDmgTaken(int skill);
 	int GetSkillDmgTaken(int skill);
 	int GetFcDamageAmtIncoming(Lua_Mob caster, int32 spell_id);
-	int GetSkillDmgAmt(uint16 skill);
+	int GetSkillDmgAmt(int skill_id);
 	void SetAllowBeneficial(bool value);
 	bool GetAllowBeneficial();
 	bool IsBeneficialAllowed(Lua_Mob target);