cmd, core/state, eth, tests, trie: improve state reader (#27428)

The state availability is checked during the creation of a state reader.

-    In hash-based database, if the specified root node does not exist on disk disk, then
    the state reader won't be created and an error will be returned.

-    In path-based database, if the specified state layer is not available, then the
    state reader won't be created and an error will be returned.

This change also contains a stricter semantics regarding the `Commit` operation: once it has been performed, the trie is no longer usable, and certain operations will return an error.

eth/protocols/snap/sync_test.go

@@ -1664,7 +1664,7 @@ func verifyTrie(db ethdb.KeyValueStore, root common.Hash, t *testing.T) {
 		t.Fatal(err)
 	}
 	accounts, slots := 0, 0
-	accIt := trie.NewIterator(accTrie.NodeIterator(nil))
+	accIt := trie.NewIterator(accTrie.MustNodeIterator(nil))
 	for accIt.Next() {
 		var acc struct {
 			Nonce    uint64
@@ -1682,7 +1682,7 @@ func verifyTrie(db ethdb.KeyValueStore, root common.Hash, t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			storeIt := trie.NewIterator(storeTrie.NodeIterator(nil))
+			storeIt := trie.NewIterator(storeTrie.MustNodeIterator(nil))
 			for storeIt.Next() {
 				slots++
 			}