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).

core/vm/runtime/runtime_test.go

@@ -95,7 +95,7 @@ func TestExecute(t *testing.T) {
 
 func TestCall(t *testing.T) {
 	db, _ := ethdb.NewMemDatabase()
-	state, _ := state.New(common.Hash{}, db)
+	state, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	address := common.HexToAddress("0x0a")
 	state.SetCode(address, []byte{
 		byte(vm.PUSH1), 10,