Upgrade Vue.js 2 to 3

[La0]

Refs #2259

This is a large work, fortunately the frontend code base is relatively small.

Steps, in successive Pull requests, following recommendations:

1. Start Vue 3 migration build to update Vue.js dependencies
   • reach step 10 where both vuex & vue-router are upgraded
2. Migrate from vuex (now deprecated) to Pinia
   • follow migration guide
   • you can probably keep everything in a single store as there are few actions
3. upgrade vue-router to support vue 3
4. Switch to vite instead of webpack for build tool as it's the recommended default now
5. Iterate over individual warnings from vue js migration build until the compat mode can be disabled