Scourge invasion undead set bonuses and item effects

[xorrbit]

Added undead set bonuses and item effects from scourge invasion event gear, this includes:

• Regalia of Undead Cleansing
• Undead Slayer's Armor
• Garb of the Undead Slayer
• Battlegear of Undead Slaying

[xorrbit]

This PR needs some work. From Lucenia on discord:

Aaaaah yeah these are fun. technically all of the mob type effects are implemented incorrectly in the classic sim

We discovered during sod that mob type effects have a special characteristic where they not only increase all damage done to the target type, but ALSO double dip on crits. That means that we actually use the attack tables to make the change properly

This is how I set up the effects in SoD using attack tables. You could skip the extra aura bit since in SoD they were procs. For you it would just be iterating over undead units, iterating over the attack tables for that unit, then multiplying both damage and crit damage
https://github.com/wowsims/sod/blob/761b4934a923f578eb429707071daea2c93d1e10/sim/shaman/item_sets_pve_phase_7.go#L74-L93