core/state: access trie through Database interface, track errors (#14589)

With this commit, core/state's access to the underlying key/value database is
mediated through an interface. Database errors are tracked in StateDB and
returned by CommitTo or the new Error method.

Motivation for this change: We can remove the light client's duplicated copy of
core/state. The light client now supports node iteration, so tracing and storage
enumeration can work with the light client (not implemented in this commit).

cmd/geth/chaincmd.go

@@ -312,7 +312,7 @@ func dump(ctx *cli.Context) error {
 			fmt.Println("{}")
 			utils.Fatalf("block not found")
 		} else {
-			state, err := state.New(block.Root(), chainDb)
+			state, err := state.New(block.Root(), state.NewDatabase(chainDb))
 			if err != nil {
 				utils.Fatalf("could not create new state: %v", err)
 			}