eth/protocols/snap: snap sync testing (#22179)

* eth/protocols/snap: make timeout configurable

* eth/protocols/snap: snap sync testing

* eth/protocols/snap: test to trigger panic

* eth/protocols/snap: fix race condition on timeouts

* eth/protocols/snap: return error on cancelled sync

* squashme: updates + test causing panic + properly serve accounts in order

* eth/protocols/snap: revert failing storage response

* eth/protocols/snap: revert on bad responses (storage, code)

* eth/protocols/snap: fix account handling stall

* eth/protocols/snap: fix remaining revertal-issues

* eth/protocols/snap: timeouthandler for bytecode requests

* eth/protocols/snap: debugging + fix log message

* eth/protocols/snap: fix misspelliings in docs

* eth/protocols/snap: fix race in bytecode handling

* eth/protocols/snap: undo deduplication of storage roots

* synctests: refactor + minify panic testcase

* eth/protocols/snap: minor polishes

* eth: minor polishes to make logs more useful

* eth/protocols/snap: remove excessive logs from the test runs

* eth/protocols/snap: stress tests with concurrency

* eth/protocols/snap: further fixes to test cancel channel handling

* eth/protocols/snap: extend test timeouts on CI

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