Remove activityInfo from cache on package uninstall

We were keeping stale activityInfo objects from
package manager after an application got uninstalled.
We also were not removing task icons from the
cache after they were removed, which meant killing an
app and then re-opening would put 2 entries in the cache
since the two had unique process IDs.

fixes: 137731960
Test: Download app from play store, open it,
go to overview and observe that correct icon showing.
Uninstall it, download same app again, open it, and
in overview confirm that correct app icon is still showing

Change-Id: Icf482b0ad0ae66c10d52547582d8eeb2a544fb88