Adds new atomic install API

This change adds the new atomic install system API to
PackageInstaller and plumbs it through to PackageManager. It also
adds support for committing multiple sessions via command line.

Bug: 109941548
Test: Manually install 2 apps from command line
Change-Id: I71d77026a55a40c76925e55e6956fb76efe16224
9 files changed