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.

core/state/snapshot/generate.go

@@ -382,8 +382,6 @@ func (dl *diskLayer) generateRange(ctx *generatorContext, trieId *trie.ID, prefi
 	}
 	var (
 		trieMore       bool
-		nodeIt         = tr.NodeIterator(origin)
-		iter           = trie.NewIterator(nodeIt)
 		kvkeys, kvvals = result.keys, result.vals
 
 		// counters
@@ -397,7 +395,12 @@ func (dl *diskLayer) generateRange(ctx *generatorContext, trieId *trie.ID, prefi
 		start    = time.Now()
 		internal time.Duration
 	)
+	nodeIt, err := tr.NodeIterator(origin)
+	if err != nil {
+		return false, nil, err
+	}
 	nodeIt.AddResolver(resolver)
+	iter := trie.NewIterator(nodeIt)
 
 	for iter.Next() {
 		if last != nil && bytes.Compare(iter.Key, last) > 0 {