* trie: make hasher parallel when number of changes are large

* trie: remove unused field dirtyCount

* trie: rename unhashedCount/unhashed

* trie:  make db insert use size instead of full data

* core/state: minor optimization in state onleaf allocation

* trie: implement dedicated committer and hasher

* trie: use dedicated committer/hasher

* trie: linter nitpicks

* core/state, trie: avoid unnecessary storage trie load+commit

* trie: review feedback, mainly docs + minor changes

* trie: start deprecating old hasher

* trie: fix misspell+lint

* trie: deprecate hasher.go, make proof framework use new hasher

* trie: rename pure_committer/hasher to committer/hasher

* trie, core/state: fix review concerns

* trie: more review concerns

* trie: make commit collapse into hashnode, don't touch dirtyness

* trie: goimports fixes

* trie: remove panics

* trie/tests: add benchmarks and update trie tests

* trie: update benchmark tests

* trie: utilize callbacks instead of amassing lists of hashes in database ref/unref

* trie: replace remaining non-callback based accesses

* add node.go unit test file node_test.go

* add node_test.go file license and rollback trie_test.go

* fix unused variable v

* trie: fix license year

Co-authored-by: Péter Szilágyi <peterke@gmail.com>

When we flush a batch of trie nodes into database during the state
sync, we should guarantee that all children should be flushed before
parent.

Actually the trie nodes commit order is strict by: children -> parent.
But when we flush all ready nodes into db, we don't need the order
anymore since

    (1) they are all ready nodes (no more dependency)
    (2) underlying database provides write atomicity

* core, trie: decode the value for storage dump

* core/state: address comment

No need to convert these types.

* all: freezer style syncing

core, eth, les, light: clean up freezer relative APIs

core, eth, les, trie, ethdb, light: clean a bit

core, eth, les, light: add unit tests

core, light: rewrite setHead function

core, eth: fix downloader unit tests

core: add receipt chain insertion test

core: use constant instead of hardcoding table name

core: fix rollback

core: fix setHead

core/rawdb: remove canonical block first and then iterate side chain

core/rawdb, ethdb: add hasAncient interface

eth/downloader: calculate ancient limit via cht first

core, eth, ethdb: lots of fixes

* eth/downloader: print ancient disable log only for fast sync

* core, eth, trie: bloom filter for trie node dedup during fast sync

* eth/downloader, trie: address review comments

* core, ethdb, trie: restart fast-sync bloom construction now and again

* eth/downloader: initialize fast sync bloom on startup

* eth: reenable eth/62 until we properly remove it

* trie: fix merkle proof

* trie: use hasher instead of allocate keccack256 every time

* trie: add comments

This PR is a more advanced form of the dirty-to-clean cacher (#18995),
where we reuse previous database write batches as datasets to uncache,
saving a dirty-trie-iteration and a dirty-trie-rlp-reencoding per block.

* trie: disable fnv64a hashing of hashes for bigcache

* trie/database: add very important period

* cmd, core, eth, trie: get rid of trie cache generations

* core, trie: get rid of remainder of cache gen boilerplate

trie/database: fix overflow in parent tracking

* trie: return hasher to pool

* trie: minor code formatting fix

The current trie memory database/cache that we do pruning on stores
trie nodes as binary rlp encoded blobs, and also stores the node
relationships/references for GC purposes. However, most of the trie
nodes (everything apart from a value node) is in essence just a
collection of references.

This PR switches out the RLP encoded trie blobs with the
collapsed-but-not-serialized trie nodes. This permits most of the
references to be recovered from within the node data structure,
avoiding the need to track them a second time (expensive memory wise).