Set ActivityInfo.resizeMode to RESIZE_MODE_RESIZEABLE by default

Previous assumption was ActivityInfo was completely initialized in
PackageParser, but that isn't the case with the ResolverActivity
whose ActivityInfo in populated in PackageManagerService.
This was causing the device to exist multi-window mode since
the default ActivityInfo.resizeMode was 0 (RESIZE_MODE_UNRESIZEABLE).

Bug: 28378995
Change-Id: I46e58d434f2a0274c461a8ff00b59ed3d2a1dd52