feature #1530 Use Symfony UX Icons (javiereguiluz)

This PR was squashed before being merged into the main branch.

Discussion
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Use Symfony UX Icons

Let's start using more UX packages in this project. I propose to use Tabler icons because we use them in all Symfony websites, in the Symfony Profiler and Toolbar, etc.

I'm pinging `@smnandre` and `@Kocal` because I have a question. I had to apply these attributes by default:

```yaml
ux_icons:
    default_icon_attributes:
        width: 1.2em
        height: 1.2em
        style: 'position: relative; top: -2px;'
```

If I don't, the icons look very small and not aligned vertically:

* The alignment is ideally solved by using `flex` in buttons and other elements that display icons + text. Since I'd like to add Twig Components here, I prefer to not change HTML/CSS much and instead, apply these attributes as a trade-off until we solve this in a better way.
* About the small icon size, I don't know why they look so small with the default `1em`. Any help is appreciated.

Thanks!

Commits
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986f239 Use Symfony UX Icons

Author: javiereguiluz

assets/app.js

@@ -1,8 +1,6 @@
 // start the Stimulus application
 import './bootstrap.js';
 import './styles/app.scss';
-import '@fortawesome/fontawesome-free/css/all.css';
-import '@fortawesome/fontawesome-free/css/v4-shims.css';
 import 'highlight.js/styles/github-dark-dimmed.css';
 import 'lato-font/css/lato-font.css';