[Spells] Implemented SPA 463 SE_SHIELD_TARGET (#4224)

SPA 463 SE_SHIELD_TARGET

Live description: "Shields your target, taking a percentage of their damage".

Only example spell on live is an NPC who uses it during a raid event "Laurion's Song" expansion. SPA 54492 'Guardian Stance' Described as 100% Melee Shielding

Example of mechanic. Base value = 70. Caster puts buff on target. Each melee hit Buff Target takes 70% less damage, Buff Caster receives 30% of the melee damage.
Added mechanic to cause buff to fade if target or caster are separated by a distance greater than the casting range of the spell. This allows similar mechanics to the /shield ability, without a range removal mechanic it would be too easy to abuse if put on a player spell. *can not confirm live does this currently

Can not be cast on self.

zone/common.h

@@ -512,6 +512,7 @@ struct StatBonuses {
 	uint8	invisibility;						// invisibility level
 	uint8	invisibility_verse_undead;			// IVU level
 	uint8	invisibility_verse_animal;			// IVA level
+	int32	ShieldTargetSpa[2];                 // [0] base = % mitigation amount, [1] buff slot
 
 	// AAs
 	int32	TrapCircumvention;					// reduce chance to trigger a trap.
@@ -657,6 +658,8 @@ namespace SBIndex {
 	constexpr uint16 COMBAT_PROC_SPELL_ID                   = 1; // SPA
 	constexpr uint16 COMBAT_PROC_RATE_MOD                   = 2; // SPA
 	constexpr uint16 COMBAT_PROC_REUSE_TIMER                = 3; // SPA
+	constexpr uint16 SHIELD_TARGET_MITIGATION_PERCENT       = 0; // SPA 463
+	constexpr uint16 SHIELD_TARGET_BUFFSLOT                 = 1; // SPA 463
 };