This PR reworks the Objective-C-based "Set Featured Image" flow in SwiftUI and introduces a few enhancements. The new implementation now completely isolated from the view controller and fits in a single file, so it's easy to follow.

Changes

• Fix layout of “Set Featured Image” button (the height was incorrect)
• Add a "More" menu for quick access to edit actions
• Add a quick way to "Replace" an image
• Add zoom transition

Technical Notes

This PR introduces new MediaPicker component for managing media sources from SwiftUI. It builds on top of the existing MediaPickerMenu, but provides a higher-level API:

 let configuration = MediaPickerConfiguration(
    sources: [.photos, .camera, .playground, .siteMedia(blog: post.blog)],
    filter: .images
)
MediaPicker(configuration: configuration, onSelection: { selection in /* ... /* ) {
    Label("Select Image", systemImage: "photo.badge.plus")
}

It also introduces SiteMediaImageView (UIKit) and SiteMediaImage (UIKit) to simplify rendering thumbnails for site media images.

Screenshots

Regression Notes

1. Potential unintended areas of impact

2. What I did to test those areas of impact (or what existing automated tests I relied on)

3. What automated tests I added (or what prevented me from doing so)

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Testing checklist:

• WordPress.com sites and self-hosted Jetpack sites.
• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• VoiceOver.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• iPhone and iPad.
• Multi-tasking: Split view and Slide over. (iPad)