Setup app to be loaded as MFE

[gciotola]

What I did

This PR aims to change the way the React app is initialized so it can be loaded as micro front-end calling an init method available from the global window.

To do so I've applied the following changes:

• Updated to the latest version of app-elements.
• Updated required node version in pnpm and ci to 20.11.0 (with other toolings that relies on package.json's engines we have a more relaxed >=18).
• Updated CI config to use latest AWS orbs
• Added rollup-plugin-external-global package to have react and react-dom as externals.
• Updated vite.config to generate manifest.json.
• Updated index.html to load React from a CDN and initialize the app via window.clApp_${appName}.init with initial settings retrieved from env vars.
• .env file is now versioned and distributed with default values (or empty, but they must exist). This is to allows vite to replace real content in the index.html (see point above).
• Updated main.tsx to use createApp method from app-elements,
• and moved all context providers from App.tsx to main.tsx to avoid unnecessary props drilling (except for routerBase).
• Removed global.d.ts since is now part of app-elements.
• Updated app home page to use HomePageLayout from app-elements.
• Updated Metrics API fetcher functions to accept a domain as an argument instead of reading it from window.clAppConfig

How to test

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests).
• Make sure to add/update documentation regarding your changes.
• You are NOT deprecating/removing a feature.