[UI] Preserve SwiftUI sizing and replacement transitions - #92

💡 Codex Review

https://github.com/NachoSoto/AsyncImageView/blob/6e01b2ec20c14b6488d2d006037bb69b154432f1/AsyncSwiftUIImageView.swift#L152
Add an actual stretch-to-fill mode

When .fill is selected for a non-square image in a differently shaped frame, aspectRatio(nil, contentMode: .fill) preserves the image's aspect ratio; it is SwiftUI's aspect-fill behavior and cannot reproduce stretch-to-bounds/UIImageView.ContentMode.scaleToFill. The image will instead extend beyond one frame dimension and either bleed or be cropped, so the legacy scale-to-fill use case described by this change still needs a distinct mode that omits the aspect-ratio modifier.

https://github.com/NachoSoto/AsyncImageView/blob/6e01b2ec20c14b6488d2d006037bb69b154432f1/AsyncSwiftUIImageView.swift#L153-L154
Base replacement animation on the incoming result

When a non-cache-hit image is currently displayed and the next result is a cache hit, changing the ID removes the old subtree using that old subtree's .easeOut transition; the incoming view's animation(nil) does not cancel the outgoing transition. The replacement can therefore still cross-fade or linger despite cache hits being intended to swap immediately, unlike AsyncImageView.updateImage; drive the whole replacement transaction from the incoming result or otherwise disable the outgoing animation for cached replacements.