move vue and vue-calendar-heatmap to webpack (#10188)

- unvendor vue and vue-calendar-heatmap
- remove unused moment.js leftover from previous heatmap version
- ensure webpack loads the full version of vue
- fix vue devmode warning related to 'searchLimit' type

I wanted to name the chunk heatmap.js but adblockers don't like that
filename [1].

[1] 3899d5dff3/easyprivacy/easyprivacy_general.txt (L2095)

webpack.config.js

@@ -204,6 +204,9 @@ module.exports = {
   },
   resolve: {
     symlinks: false,
+    alias: {
+      vue$: 'vue/dist/vue.esm.js', // needed because vue's default export is the runtime only
+    },
   },
   watchOptions: {
     ignored: [