Step 2 - Setup `useFakeDate` by default in Jest

• Step 1 - Add fake_date test helper
• Step 2 - Setup useFakeDate by default in Jest
• Step 3 - Update default fake date to match rspec fixtures
• Step 3 - Add helper for useFixturesFakeDate

What does this MR do?

This MR sets up useFakeDate by default in our Jest environment

ee/spec/frontend/analytics/code_review_analytics/components/merge_request_table_spec.js

@@ -3,16 +3,12 @@ import { createLocalVue, mount } from '@vue/test-utils';
 import Vuex from 'vuex';
 import MergeRequestTable from 'ee/analytics/code_review_analytics/components/merge_request_table.vue';
 import createState from 'ee/analytics/code_review_analytics/store/modules/merge_requests/state';
-import { useFakeDate } from 'helpers/fake_date';
 import { mockMergeRequests } from '../mock_data';
 
 const localVue = createLocalVue();
 localVue.use(Vuex);
 
 describe('MergeRequestTable component', () => {
-  // Some tests are dependent that the year is >= 2020
-  useFakeDate(2020, 6, 6);
-
   let wrapper;
   let vuexStore;