Make static CSS file / disable style injection the default

[joshwooding]

We've had a lot of requests to support SSR (#2505, #2499), had internal conversations around RSC and the ecosystem's move away from runtime CSS injection, as well as inquiries into module federation support.

The best way of achieving this is moving away from useComponentCSSInjection to require importing CSS files. I've explored that here: #2508 as part of our build tool migration.

To achieve this we should:

• Migrate our build tooling and provide a CSS bundle per package.
• Investigate providing a CSS file per component.

Challenges:

• Figure out how this affects desktop support

This work should be done in 1.0 of Salt with CSS imports being the default in 2.0