[Fluent2 Tokens] Convert Notification to use ShadowInfo token

[mischreiber]

Platforms Impacted

• [x] iOS
• [ ] macOS

Description of changes

This PR combines all the individual shadow token values into a single ShadowInfo property for customization.

Verification

Verified that shadows look the same before and after.

Also checked binary size! Got a solid 27 kB improvement 🥳

Before	After
33,357 kB	33,329 kB

Pull request checklist

This PR has considered:

• [x] Light and Dark appearances
• [ ] iOS supported versions (all major versions greater than or equal current target deployment version)
• [ ] VoiceOver and Keyboard Accessibility
• [ ] Internationalization and Right to Left layouts
• [ ] Different resolutions (1x, 2x, 3x)
• [ ] Size classes and window sizes (iPhone vs iPad, notched devices, multitasking, different window sizes, etc)
• [ ] iPad Pointer interaction
• [x] SwiftUI consumption (validation or new demo scenarios needed)
• [ ] Objective-C exposure (provide it only if needed)

Microsoft Reviewers: Open in CodeFlow

[huwilkes]

Should this be going in to fluent2-tokens or main?

[mischreiber]

Should this be going in to fluent2-tokens or main?

It's an API breaking change, so I'm gonna stage it to fluent2-tokens and it can be brought to main as part of the big ControlTokenSet merge (0.8 release).