Support data plane RBAC for Gremlin API (#2182)

* Refactor logic for determining if we should use data plane RBAC to a
common function.

* Support RBAC for gremlin API.

* Refactor to use common function.

* Fix unit tests.

* Move test function inside test scope.

* Minor clean ups.

* Reinstate utf8ToB64 function in case this breaks a corner case.

src/Explorer/Graph/GraphExplorerComponent/GremlinSimpleClient.test.ts

@@ -5,11 +5,11 @@
 
 import * as sinon from "sinon";
 import {
+  GremlinRequestMessage,
+  GremlinResponseMessage,
   GremlinSimpleClient,
   GremlinSimpleClientParameters,
   Result,
-  GremlinRequestMessage,
-  GremlinResponseMessage,
 } from "./GremlinSimpleClient";
 
 describe("Gremlin Simple Client", () => {