+ client: Allow Fastest IP address and Parallel requests to toggle each other: Merge pull request #619 in DNS/adguard-home from feature/1678 to master

Close #1678

Squashed commit of the following:

commit 9251ed0f1b58426104d1b9bdaa4b7af5f92be83e
Author: ArtemBaskal <a.baskal@adguard.com>
Date:   Thu May 21 18:25:18 2020 +0300

    + client: Allow `Fastest IP address` and `Parallel requests` to toggle each other

client/src/helpers/constants.js

@@ -374,3 +374,8 @@ export const ACTION = {
     block: 'block',
     unblock: 'unblock',
 };
+
+export const DNS_REQUEST_OPTIONS = {
+    PARALLEL_REQUESTS: 'parallel_requests',
+    FASTEST_ADDR: 'fastest_addr',
+};