[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/perl_mob.cpp

@@ -2517,7 +2517,7 @@ void Perl_Mob_ApplySpellBuff(Mob* self, int spell_id, int duration) // @categori
 	self->ApplySpellBuff(spell_id, duration);
 }
 
-int Perl_Mob_GetSkillDmgAmt(Mob* self, uint16 skill_id)
+int Perl_Mob_GetSkillDmgAmt(Mob* self, int skill_id)
 {
 	return self->GetSkillDmgAmt(skill_id);
 }