Improve Imitator role balance

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Currently, Imitator is an imbalanced role because it ignores the maximum ability uses on certain powerful roles. This PR adjusts the role so that it respects both:

• The ability uses remaining for the dead role when they died (therefore enforcing an actual maximum number of uses of that ability per game).
• The ability uses remaining for the imitated role when a meeting is called.

As it stands, Engineer is an unplayable role when in a lobby with Imitator, because if the Imitator grabs their role, their uses of Fix are refreshed every meeting, allowing them to fix basically every sabotage the impostors call instantly for the rest of the game or until they are also killed.

This is clearly not the intention behind giving the Engineer a limited number of fixes, and makes life unfairly miserable for the impostors. This corrects the balance when the roles are combined. If the Engineer used all their fixes before dying, the Imitator gets none. If they had some remaining, the Imitator may use them, but they can only use the amount they had remaining.

Note: Tracker is exempted because their uses are intended to refresh every meeting.

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Updated for v5.0.3

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Updated for v5.0.4