WIP: PhoshHome: Reset overview when folding ends instead of when unfolding starts

Resetting the app grid from filtered state can take a noticeable amount of time. Do it when folding animation ends, when it's far less likely that the user wants to interact with the shell, rather than when unfolding animation starts, which is almost guaranteed to be done because of user action. Thanks to that the shell can respond faster.

WIP only because it's on top of !734 (merged) to keep things simple.