Motivation:
Client code sometimes struggle with managing their buffer reference counts correctly,
so there's a use case for buffers that are deallocated by cleaners.
Modification:
Add another allocator, directWithCleaner, which registers all the native memory segments with cleaners.
Result:
It's possible to get unpooled direct buffers, that are automatically deallocated by a cleaner if they are no longer strongly
referenced.
The same is not necessary for heap buffers, since they can be garbage collected like normal objects.
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