Fix(db/creature) black temple illidari assassin riposte ability missing

[Carriola-wotlk]

Changes Proposed:

This PR proposes changes to:

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

Issues Addressed:

• Closes [Black Temple] Illidari Assassin: some abilities are missing. #19876
• Closes [Black Temple] Trash Mobs - Illidari Assassin missing spells chromiecraft/chromiecraft#7334

Actually, the bug is a bit different from how it was described in this ticket. The first spawned Assassin only casts Paralyzing Poison and Vanish abilities (and doesn't cast Riposte). The other 3 spawns don't cast anything, they only perform melee attacks.

So in the bugfix, I didn't modify the existing spells, but I added new row for Riposte. As for the timers, I checked the logs here: link. It seems that the first Riposte is cast within 15 seconds. And then I modified flags_extra by setting DONT_OVERRIDE_SAI_ENTRY (so that all 4 NPCs use the SAI).

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.)
• The changes promoted by this pull request come partially or entirely from another project (cherry-pick). Cherry-picks must be committed using the proper --author tag in order to be accepted, thus crediting the original authors, unless otherwise unable to be found

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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[Nyeriah]

Use the bitwise method to update bitmasks e.g

To add:
flags_extra = flags_extra | $flag

To remove:
flags_extra = flags_extra &~ $flag

[Rorschach91]

I tested the script and It works. It can be merged for me.