core, eth, les, tests, trie: abstract node scheme (#25532)

This PR introduces a node scheme abstraction. The interface is only implemented by `hashScheme` at the moment, but will be extended by `pathScheme` very soon.

Apart from that, a few changes are also included which is worth mentioning:

-  port the changes in the stacktrie, tracking the path prefix of nodes during commit
-  use ethdb.Database for constructing trie.Database. This is not necessary right now, but it is required for path-based used to open reverse diff freezer

core/blockchain_reader.go

@@ -29,6 +29,7 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 // CurrentHeader retrieves the current head header of the canonical chain. The
@@ -375,6 +376,11 @@ func (bc *BlockChain) TxLookupLimit() uint64 {
 	return bc.txLookupLimit
 }
 
+// TrieDB retrieves the low level trie database used for data storage.
+func (bc *BlockChain) TrieDB() *trie.Database {
+	return bc.triedb
+}
+
 // SubscribeRemovedLogsEvent registers a subscription of RemovedLogsEvent.
 func (bc *BlockChain) SubscribeRemovedLogsEvent(ch chan<- RemovedLogsEvent) event.Subscription {
 	return bc.scope.Track(bc.rmLogsFeed.Subscribe(ch))