Progress towards staging ASECs.

Move location selection logic into shared PackageHelper location,
and share it between DCS and PackageInstaller.  Fix bugs related to
installed footprint calculation; always count unpacked native libs.

Have PMS do its own threshold checking, since it's fine to stat
devices.  PMS only ever deleted staging ASECs, so move that logic
into installer and nuke unclaimed staging ASECs.  Allocate legacy
ASEC names using PackageInstaller to make sure they don't conflict
with sessions.

Start wiring up session to allocate ASEC and pass through staged
container for installation.

Fix bug to actually delete invalid cluster-style installs.

Bug: 16514385
Change-Id: I325e0c4422fc128398c921ba45fd73ecf05fc2a9
9 files changed