This PR refactors the `nodeSet` structure in the path database to use
separate maps for account and storage trie nodes, resulting in
performance improvements. The change maintains the same API while
optimizing the internal data structure.
This pull request ports some changes from the main state snapshot
integration one, specifically introducing the flat state tracking in
pathdb.
Note, the tracked flat state changes are only held in memory and won't
be persisted in the disk. Meanwhile, the correspoding state retrieval in
persistent state is also not supported yet. The states management in
disk is more complicated and will be implemented in a separate pull
request.
Part 1: https://github.com/ethereum/go-ethereum/pull/30752
