Replace InternalNode's separate left and right fields with a
children [2]BinaryNode array, where children[0] = left and
children[1] = right. The bit extracted from the key (always 0 or 1)
maps directly to the array index, eliminating duplicated if/else
blocks in GetValuesAtStem, InsertValuesAtStem, and the iterator.
Net reduction of ~100 lines across 8 files.
This is an optimization that existed for verkle and the MPT, but that
got dropped during the rebase.
Mark the nodes that were modified as needing recomputation, and skip the
hash computation if this is not needed. Otherwise, the whole tree is
hashed, which kills performance.
Implement the binary tree as specified in [eip-7864](https://eips.ethereum.org/EIPS/eip-7864).
This will gradually replace verkle trees in the codebase. This is only
running the tests and will not be executed in production, but will help
me rebase some of my work, so that it doesn't bitrot as much.
---------
Signed-off-by: Guillaume Ballet
Co-authored-by: Parithosh Jayanthi <parithosh.jayanthi@ethereum.org>
Co-authored-by: rjl493456442 <garyrong0905@gmail.com>
