Wire call to suspend a package

Adds APIs in DevicePolicyManager and PackageManager for allowing
a device admin to suspend a package. PackageManagerService sets
or unsets a new PackageUserState 'suspended' setting. Terminal
command to suspend/unsuspend has been added via
PackageManagerShellCommand (as root).

Next steps:
* use the new 'suspended' setting for denying access to start app
(probably in ActivityStackSupervisor)
* broadcast a PACKAGE_(UN)SUSPENDED intent for launchers to pick up
* remove app from recents (go further and kill it if it is running)
* erase existing notifications for this app

Bug: 22776576
Change-Id: I718b3498f6a53cc0c6fdfb6d15031e53ddca4353