fix(Scripts/Spell): Priest shadowfiend attack and Shadowfiend Death proc

[sogladev]

Changes Proposed:

This PR proposes changes to:

• Core (units, players, creatures, game systems).
• Scripts (bosses, spell scripts, creature scripts).
• Database (SAI, creatures, etc).

removes petAI hack and move auras/proc handling to DB/spellscript

note that when targeting a neutral mob and cast shadowfiend. It does not attack. If right-click, and then summon, it does attack. SUMMON_PROP_FLAG_ASSIST_COMBAT_SUMMON is not set. Feral Spirits, Treants, Fire Elemental have the same behavior. I think this is correct behavior for a guardian

Issues Addressed:

• Closes Shadowfiend does not stay aggressive upon summon chromiecraft/chromiecraft#4945
• Closes 💰50$ Bounty - [Priest] Shadowfiend after being summoned will chase the summoner instead of attacking the target #16741

SOURCE:

The changes have been validated through:

• Live research (checked on live servers, e.g Classic WotLK, Retail, etc.)
• Sniffs (remember to share them with the open source community!)
• Video evidence, knowledge databases or other public sources (e.g forums, Wowhead, etc.)
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cp Priest: Implement missing glyphs and move existing to spell cmangos/mangos-wotlk@3b1dfe0

Tests Performed:

This PR has been:

• Tested in-game by the author.
• Tested in-game by other community members/someone else other than the author/has been live on production servers.
• This pull request requires further testing and may have edge cases to be tested.

How to Test the Changes:

• This pull request can be tested by following the reproduction steps provided in the linked issue
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regression:

1. .tele marrowgar
2. instakill to proc mana regen effect

Known Issues and TODO List:

• 57989 is a permanent aura.
  unused spell 41967 3s. Server-side spell that applies 57989 after 3 seconds? To prevent insta death from giving mana?
  https://wowgaming.altervista.org/aowow/?spell=41967
• save autocast of spells, and? "aggressive" status on summon with summon property SUMMON_PROP_FLAG_SAVE_PET_AUTOCAST cmangos/mangos-wotlk@ca466c3

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