[Multi-user] add PackageInstaller.installExistingPackage with IntentSender which is fired only

after the asynchronous restore is complete

This is a better alternative to the existing synchronous PackageManager.installExistingPackage
method where the restore operation happens asynchronously but the method itself will return
success before the restore finishes.

Bug: 122881085

Test: 1) cts-tradefed run cts -m CtsBackupHostTestCases
-t android.cts.backup.ProfileKeyValueBackupRestoreHostSideTest
2) atest RunBackupFrameworksServicesRoboTests
3) Install Hangouts on work profile. Then install on primary profile, backup and uninstall.
Now install again and immediately hit Open. Before this change, the app will crash after a few
seconds (when the background restore operation finishes). With this change and a corresponding
Play Store change to use this new method, Open shows up only after restore has finished so the
app doesn't crash.

Change-Id: I5d2e1f3bb5509894bedd6bbcfac32ed6cf946a80