Don't display expired dependency proxy images

Problem

We've moved Dependency Proxy blob/manifest deletion to a background job, so purging the cache, or using the Dependency Proxy cleanup policy will mark the records as expired, but deletion may not happen until later.

While expired images are not used when users pull from the dependency proxy, they are still displayed in the UI.

Solution

We should either:

1. Only display active records in the UI
2. Display expired/pending deletion records grayed out with some indicator that they are queued for deletion.