Fix Metrics environments dropdown

Also bring back EE dashboard component

app/assets/javascripts/monitoring/components/dashboard.vue

@@ -221,6 +221,7 @@ export default {
           <gl-dropdown-item
             v-for="environment in store.environmentsData"
             :key="environment.id"
+            :href="environment.metrics_path"
             :active="environment.name === currentEnvironmentName"
             active-class="is-active"
             >{{ environment.name }}</gl-dropdown-item

app/assets/javascripts/monitoring/monitoring_bundle.js

 import Vue from 'vue';
 import { parseBoolean } from '~/lib/utils/common_utils';
-import Dashboard from './components/dashboard.vue';
+import Dashboard from 'ee_else_ce/monitoring/components/dashboard.vue';
 
 export default (props = {}) => {
   const el = document.getElementById('prometheus-graphs');

changelogs/unreleased/60687-enviro-dropdown.yml

+---
+title: Fix Metrics Environments dropdown
+merge_request:
+author:
+type: fixed

spec/javascripts/monitoring/dashboard_spec.js

@@ -175,7 +175,7 @@ describe('Dashboard', () => {
 
       setTimeout(() => {
         const dropdownItems = component.$el.querySelectorAll(
-          '.js-environments-dropdown .dropdown-item[active="true"]',
+          '.js-environments-dropdown .dropdown-item.is-active',
         );
 
         expect(dropdownItems.length).toEqual(1);