fix(Core/Creature): Use minimum template level instead of current level for leash timer.

[heyitsbench]

Changes Proposed:

This PR proposes changes to:

• Core (units, players, creatures, game systems).

Issues Addressed:

• Progresses Creatures leash system not blizzlike #5116

SOURCE:

The changes have been validated through:

• Video evidence, knowledge databases or other public sources (e.g forums, Wowhead, etc.)

Tests Performed:

This PR has been:

• 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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