use encodeImage ref hash to replace AnimatedImageResult's hashcode as…

[WhileCrow]

I create a issue a few days ago, #2605, I'm kind of dying to know if this is a real problem. If this is a problem, is my way of fixing it appropriate?

Test Plan

Load the same GIF multiple times, check [ if the cache correctly increase by observing the memory of the Android Profiler ] and [ if the count of entries in the cache pool correctly increase].

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