[SIP-4] replace SQL Lab ajax calls with SupersetClient (#5896)

* [superset-client] replace sqllab ajax calls with SupersetClient

* [superset-client][sqllab] replace more misc ajax calls

* [superset-client][tests] call setupSupersetClient() in test shim

* [superset-client] replace more sqllab ajax calls and fix tests

* [superset-client][tests] remove commented lines

* [sqllab][superset-client] fix eslint and tests, add better error handling tests.

* [superset-client] fix tests from rebase

* [cypress][sqllab][superset-client] fix

* [superset-client] use Promises not callbacks in getShortUrl calls

* [superset-client][short-url] don't stringify POST

* [superset-client][short-url][cypress] add data-test attribute for more reliable test

* [cypress] remove .only() call

superset/assets/spec/javascripts/explore/chartActions_spec.js

@@ -2,7 +2,6 @@ import fetchMock from 'fetch-mock';
 import sinon from 'sinon';
 
 import { Logger } from '../../../src/logger';
-import setupSupersetClient from '../../helpers/setupSupersetClient';
 import * as exploreUtils from '../../../src/explore/exploreUtils';
 import * as actions from '../../../src/chart/chartAction';
 
@@ -17,7 +16,6 @@ describe('chart actions', () => {
   };
 
   beforeAll(() => {
-    setupSupersetClient();
     setupDefaultFetchMock();
   });