Update Notification to make default action optional

[huwilkes]

Platforms Impacted

• [x] iOS
• [ ] macOS

Description of changes

The UIKit notification had a default action by default, so I added that back in to the SwiftUI one, but now we want that to be optional. Also cleaned up additional bools left in the style.

Verification

Before	After

Pull request checklist

This PR has considered:

• [ ] 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)
• [x] Objective-C exposure (provide it only if needed)

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