Grant Device ID access to PO/DO delegates

Let the delegated certificate installer access device identifiers
(serial number, IMEI, meid) via the standard platform APIs.

This makes sense since the DO/PO can already access Device IDs and
there's no technical barrier from the DO/PO to send the Device IDs to
the app it nominated as the delegate.

To make things simpler for the delegate and DPC, let the delegate access
the Device IDs directly.

Bug: 120616022
Test: atest CtsDevicePolicyManagerTestCases:com.android.cts.devicepolicy.MixedDeviceOwnerTest#testDelegatedCertInstallerDirectly
Test: atest CtsDevicePolicyManagerTestCases:com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testDelegatedCertInstallerDirectly
Change-Id: I0c996eeb0d35e99821ca3dcfe1afda01cd5ceb2f