Improve the way we are testing JS assets (E2E, real browers, ...) #3007
Description
Following the attempt to use tsdown to build our dependencies (#2935) (which will re-happens again in #3006).
When I worked on integrating tsdown, the generated code was broken when dealing with static class properties. It was not detected by our JS tests CI jobs, since it only test source files on a Node.js platform.
The Turbo E2E tests using Panther (and so a real browser) were failing by luck, and manual testing confirmed me that dist files were broken.
We need to add E2E tests based on a real Symfony app, using local UX packages, and with lowest supported browsers (with Baseline / Browserlist?) + latest browsers.