changed the sam cooldown to be a general cooldown function and added a
missilesilo cooldown
The function either adds the current tick as the starting point of the
cooldown or sets the cooldown to null and updates the unit. That way
getcooldown function can be used to get back the tick the cooldown was
started and can be compared to the cooldown set in the config.
changed the sam test / added a missilesilo test
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Co-authored-by: evanpelle <evanpelle@gmail.com>
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