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.
2 jobs for improve-uninstall-ux in 4 minutes and 36 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #789757
debian-stable-x86_64

00:03:00

failed #789756
fedora-x86_64

00:04:36

 
Name Stage Failure
failed
fedora-x86_64 Build
Uploading artifacts...
_build/config.h: found 1 matching files

_build/meson-logs: found 4 matching files

_build/fedora-x86_64-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=789756 responseStatus=201 Created token=a7gBy1ah
Uploading artifacts...
_build/fedora-x86_64-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=789756 responseStatus=201 Created token=a7gBy1ah
ERROR: Job failed: exit code 1