* eth/protocols: persist received state segments

* core: initial implementation

* core/state/snapshot: add tests

* core, eth: updates

* eth/protocols/snapshot: count flat state size

* core/state: add metrics

* core/state/snapshot: skip unnecessary deletion

* core/state/snapshot: rename

* core/state/snapshot: use the global batch

* core/state/snapshot: add logs and fix wiping

* core/state/snapshot: fix

* core/state/snapshot: save generation progress even if the batch is empty

* core/state/snapshot: fixes

* core/state/snapshot: fix initial account range length

* core/state/snapshot: fix initial account range

* eth/protocols/snap: store flat states during the healing

* eth/protocols/snap: print logs

* core/state/snapshot: refactor (#4)

* core/state/snapshot: refactor

* core/state/snapshot: tiny fix and polish
Co-authored-by: rjl493456442 <garyrong0905@gmail.com>

* core, eth: fixes

* core, eth: fix healing writer

* core, trie, eth: fix paths

* eth/protocols/snap: fix encoding

* eth, core: add debug log

* core/state/generate: release iterator asap (#5)

core/state/snapshot: less copy

core/state/snapshot: revert split loop

core/state/snapshot: handle storage becoming empty, improve test robustness

core/state: test modified codehash

core/state/snapshot: polish

* core/state/snapshot: optimize stats counter

* core, eth: add metric

* core/state/snapshot: update comments

* core/state/snapshot: improve tests

* core/state/snapshot: replace secure trie with standard trie

* core/state/snapshot: wrap return as the struct

* core/state/snapshot: skip wiping correct states

* core/state/snapshot: updates

* core/state/snapshot: fixes

* core/state/snapshot: fix panic due to reference flaw in closure

* core/state/snapshot: fix errors in state generation logic + fix log output

* core/state/snapshot: remove an error case

* core/state/snapshot: fix condition-check for exhausted snap state

* core/state/snapshot: use stackTrie for small tries

* core/state/snapshot: don't resolve small storage tries in vain

* core/state/snapshot: properly clean up storage of deleted accounts

* core/state/snapshot: avoid RLP-encoding in some cases + minor nitpicks

* core/state/snapshot: fix error (+testcase)

* core/state/snapshot: clean up tests a bit

* core/state/snapshot: work in progress on better tests

* core/state/snapshot: polish code

* core/state/snapshot: fix trie iteration abortion trigger

* core/state/snapshot: fixes flaws

* core/state/snapshot: remove panic

* core/state/snapshot: fix abort

* core/state/snapshot: more tests (plus failing testcase)

* core/state/snapshot: more testcases + fix for failing test

* core/state/snapshot: testcase for malformed data

* core/state/snapshot: some test nitpicks

* core/state/snapshot: improvements to logging

* core/state/snapshot: testcase to demo error in abortion

* core/state/snapshot: fix abortion

* cmd/geth: make verify-state report the root

* trie: fix failing test

* core/state/snapshot: add timer metrics

* core/state/snapshot: fix metrics

* core/state/snapshot: udpate tests

* eth/protocols/snap: write snapshot account even if code or state is needed

* core/state/snapshot: fix diskmore check

* core/state/snapshot: review fixes

* core/state/snapshot: improve error message

* cmd/geth: rename 'error' to 'err' in logs

* core/state/snapshot: fix some review concerns

* core/state/snapshot, eth/protocols/snap: clear snapshot marker when starting/resuming snap sync

* core: add error log

* core/state/snapshot: use proper timers for metrics collection

* core/state/snapshot: address some review concerns

* eth/protocols/snap: improved log message

* eth/protocols/snap: fix heal logs to condense infos

* core/state/snapshot: wait for generator termination before restarting

* core/state/snapshot: revert timers to counters to track total time
Co-authored-by: Martin Holst Swende <martin@swende.se>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>