Refactor (Scripts/Spells) Check for existence of AD debuff instead of adding a custom cooldown to heal

[Tereneckla]

Changes Proposed:

This PR proposes changes to:

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

If your pull request promotes complex changes that require a detailed explanation, please describe them in detail specifying what your solution is and what is it meant to address.

Issues Addressed:

• Maybe (probably not) 💰100$ Bounty - [Paladin] Ardent Defender dual spec issue #16954
• Ardent Defender Not Working chromiecraft/chromiecraft#5852

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
• This pull request requires further testing. Provide steps to test your changes. If it requires any specific setup e.g multiple players please specify it as well.

Known Issues and TODO List:

• [ ]
• [ ]

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