Add getBindDeviceAdminTargetUsers API

Add getBindDeviceAdminTargetUsers API. To be used
for the device or profile owner in a COMP setup to
know the UserHandle of their instance running on
the other profile.

Bug: 31952368,33033966
Test:  cts-tradefed run cts --module DevicePolicyManager --test com.android.cts.devicepolicy.DeviceOwnerPlusManagedProfileTest

Change-Id: I05c9ac0f6c3cdce1ec17cf2910ca7a7214064af2