This reverts commit 168ba7960c.
It seems, there are some problems with it:
`2020-12-25T18:13:07.476+0300 WARN blockQueue: failed adding block into the blockchain {"error": "error while trying to apply MPT changes: unexpected EOF", "blockHeight": 9729, "nextIndex": 9730}`
Running time becomes faster under high load while staying the same in
the average case.
Memory allocation done in `Trie` goes down by about ~10% (even more,
actually).
Because trie size is rather big, it can't be stored in memory.
Thus some form of caching should also be implemented. To avoid
marshaling/unmarshaling of items which are close to root and are used
very frequenly we can save them across the persists.
This commit implements pruning items at the specified depth,
replacing them by hash nodes.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
MPT is a trie with a branching factor = 16, i.e. it consists of sequences in
16-element alphabet.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
