details: Keep spinner spinning while refreshing info after uninstall

After removing an app, its status changes to "UNKNOWN" while the
information is refreshed to see if the app is available for reinstall.
Especially with Flathub, this can leave quite a big gap (longer than it
takes to actually uninstall the app) where nothing is happening and the
user receives no visual feedback.

During this gap, instead keep the spinner visible and spinning, and
display "Cleaning up..." in the progress label. "Cleaning up" seems a
reasonable description for this stage that's not overly technical or
exposes details that the user isn't interested in.
5 jobs for improve-uninstall-ux in 4 minutes and 17 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #524935
debian-stable-x86_64

00:01:26

passed #524940
fedora-x86_64

00:02:51

failed #524893
debian-stable-x86_64

00:00:57

failed #524936
fedora-x86_64

00:02:54

failed #524892
fedora-x86_64

00:02:54