isDecodedImageCacheHit function
Whether status is a decoded Flutter ImageCache hit (image.source=memory).
In-flight loads are ImageCacheStatus.pending and also ImageCacheStatus.live,
so keepAlive || live is not enough — a second widget joining a download
would be mislabeled as a memory hit.
Implementation
bool isDecodedImageCacheHit(ImageCacheStatus status) =>
!status.pending && (status.keepAlive || status.live);