Make DPM#checkDeviceIdentifierAccess a SystemApi

The device identifier check is performed within Telephony; one of
the checks uses a hidden method within DevicePolicyManager to perform
a device / profile owner access check. In order for Telephony to
invoke this method as a mainline module it must be made into a
SystemApi.

Fixes: 145163986
Test: atest DeviceOwnerTest#testDeviceOwnerCanGetDeviceIdentifiers
Test: atest DeviceOwnerTest#testDeviceOwnerCannotGetDeviceIdentifiersWithoutPermission
Test: atest ManagedProfileTest#testProfileOwnerOnPersonalDeviceCannotGetDeviceIdentifiers
Test: atest CtsDevicePolicyManagerTestCases:com.android.cts.devicepolicy.OrgOwnedProfileOwnerTest#testProfileOwnerCannotGetDeviceIdentifiersWithoutPermission
Test: atest CtsDevicePolicyManagerTestCases:com.android.cts.devicepolicy.OrgOwnedProfileOwnerTest#testProfileOwnerCanGetDeviceIdentifiers
Test: atest TelephonyPermissionsTest
Change-Id: Ica015f848209fc693a44fa019b25796260191e64