Start using CSS modules

[GerardasB]

Is your feature request related to a problem? Please describe.

Some of the consumers are still targeting internal AppUI class names. Utilizing CSS modules would prevent that.

Describe the Solution you'd like

Start using CSS modules in AppUI components. This can be an incremental effort since some of the components target elements outside of the component scope.

Describe alternatives you've considered

No response

Additional context

Our consumers are already using build tools that support building SCSS files.
Most bundlers should support CSS modules out of the box, however, it would be safer to introduce CSS modules with a new major release.

[GerardasB]

We will not include this feature in AppUI 5.0 because it introduces additional, non-standard, and bundler-specific requirements for our users. Ideally, CSS should be delivered separately or loaded through standard JavaScript methods. While CSS modules can be utilized as an internal build step, this approach falls outside the scope of this release. +@mayank99