fix: call delete instead of free in imagefetcher

[WoLewicki]

Summary:

I've been digging into memleaks in RN for some time and noticed that instances of FabricUIManager are leaking on reload action even on an empty app. I managed to pinpoint it to ContextContainer (which holds FabricUIManager on the cpp side) not being deallocated after reload. After much much digging (since contextContainer is passed around in many places) I found that destructor of ImageFetcher never runs on reload, and its instance holds contextContainer. It turns out that ImageManager, which holds ImageFetcher, was calling free instead of delete and the former does not call destructor. After applying it, contextContainer does not leak making FabricUIManager instances not to leak too 🎉.

Changelog:

[ANDROID] [FIXED] - Change free to delete to call destructor of ImageFetcher and release contextContainer.

Test Plan:

Run empty RN app in AS, do reload multiple times and see in AS profiler that instances of FabricUIManager are kept in memory without this change.

[javache]

Great find!

[facebook-github-bot]

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