Add getProfileParentId (1/2)

Bluetooth service needs to natively access id of parent profile. Add
method exposing it.

Test: cts-tradefed run cts-dev -m DevicePolicyManager --test
com.android.cts.devicepolicy.ManagedProfileTest#testBluetooth
Bug: 69284968
Change-Id: I697906f2959b0736c1d3cc6af7560c27d77ce11b