bug(ios): no visual indication of delay in processing downloaded packages

Noticed when analyzing https://github.com/keymanapp/keyboards/issues/2214.

> I'm not getting a reproduction for this issue now. Granted, it seems that the package installer loaded rather slowly at first - I thought I reproduced it earlier, went to investigate further via iOS simulator... but when I returned to the reproducing device, the package installer was waiting for me.

The fact that I thought I succeeded because of a significant delay is a UX deficiency.

Note that we've always assumed that there will be no significant delay in "unpacking" the package when anticipating follow-through for installation. We only prompt for installation when "unpacking" is successful, but we dismiss the keyboard search as soon as the download succeeds. It _shouldn't_ take a significant amount of time to "unpack", but maybe there can be a delay in that process somehow - and we don't have any visual indicators should it occur. On Simulator, it did seem like there was a minor delay of a couple of seconds for that issue's keyboard, even after having downloaded it previously on the emulated device.

The downloaded package is only 3.3 MB - it shouldn't take long to unpack the file, though it is a notably complex keyboard with many, many custom layers - it's in the same class as `gff_amharic` in that regard.