Convert contribution analytics charts to Vue

What does this MR do and why?

Related issue: #375999 (closed)

Combines the three Contribution Analytics charts into a single Vue app, as opposed to three separate Vue/HAML hybrids like it currently is. The logic in contribution_analytics_bundle.js was migrated to new Vue components and a shared utils.js file. Headers & description were removed from show.html.haml and also added to these new components

Screenshots or screen recordings

UI should look the same before/after this change

How to set up and validate locally

1. Navigate to http://gdk.test:3000/dashboard/groups
2. Select a group
3. In the sidebar: Analytics -> Contribution

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

ee/app/assets/javascripts/analytics/contribution_analytics/components/base.vue

+<script>
+import PushesChart from './pushes_chart.vue';
+import MergeRequestsChart from './merge_requests_chart.vue';
+import IssuesChart from './issues_chart.vue';
+
+export default {
+  name: 'ContributionAnalyticsBase',
+  components: {
+    PushesChart,
+    MergeRequestsChart,
+    IssuesChart,
+  },
+};
+</script>
+<template>
+  <div>
+    <pushes-chart />
+    <merge-requests-chart />
+    <issues-chart />
+  </div>
+</template>