rpc: personal_listWallets (#748)

* Problem: need to add JSON-RPC endpoint personal_listWallets

Closes #745

* wallet level that manages accounts is not supported by keyring interface, will return nil

* changelog entry

* fix lint failure by exposing RawWallet as public

* fix notes typo

tests/rpc/personal_test.go

@@ -152,3 +152,11 @@ func TestPersonal_InitializeWallet(t *testing.T) {
 	_, err := CallWithError("personal_initializeWallet", []interface{}{""})
 	require.Equal(t, "smartcard wallet not supported yet", err.Error())
 }
+
+func TestPersonal_ListWallets(t *testing.T) {
+	rpcRes := Call(t, "personal_listWallets", []interface{}{})
+	var res []hexutil.Bytes
+	err := json.Unmarshal(rpcRes.Result, &res)
+	require.NoError(t, err)
+	require.Equal(t, ([]hexutil.Bytes)(nil), res)
+}