snapshot, trie: fixed typos, mostly in snapshot pkg (#22133)

core/state/snapshot/conversion.go

core/state/snapshot/difflayer.go

core/state/snapshot/difflayer_test.go

core/state/snapshot/disklayer.go

core/state/snapshot/disklayer_test.go

core/state/snapshot/iterator.go

core/state/snapshot/iterator_binary.go

core/state/snapshot/iterator_fast.go

core/state/snapshot/snapshot.go

trie/database.go