Off-heap (direct) entry array

[liran-funaro]

• Refactor chunks/entry-array: put only the array access logic into EntryArray and the rest of the logic into Chunk.
• Add support for both EntryArrayHeap and EntryArrayDirect implementing EntryArray interface.
• Add OakSharedConfig to pass Oak configuration between instances of InternalOak and Chunks.
• Fix memory-leak in unit tests

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[liran-funaro]

@sanastas

we have no good separation between Hash logic and Map logic

I think it is possible to attain this separation with not too much effort. If you find methods that should be moved like the ones you already mentioned, then let me know. Anyway, I won't start applying the changes you requested and merging with the master until we feel confident that we want to go ahead with this change.

[sanastas]

I want to ask @boris-kap to make the review to this PR as well, so we have more then one opinion.

[liran-funaro]

Broke down into number of PRs and rethink chunk/array design