Storage methods using IDs, update listeners.

Add StorageManager methods that work with Disk and Volume IDs instead
of paths which can change over time.  For example, a freshly formatted
volume has a different UUID and mount point, even though it's the same
volume.

Update StorageEventListener to be all one-way calls to avoid blocking
while dispatching events.  Add new listener method for Volume-level
state changes.  The existing state method will remain focused on the
per-user state reflected by StorageVolume.  Switch listeners over to
using the more robust RemoteCallbackList pattern under the hood.

Change external ASEC scanning logic in PackageManagerService to be
driven by listener events, instead of explicit MountService calls.

Bug: 19993667
Change-Id: I57c505de260ff1762a78d70d15f1892f40229210