Add test case for getNetworkSlicingConfiguration()

Bug: 178075247
Test: run "atest TelephonyManagerTest#testGetNetworkSlicingConfiguration"
[1/1] android.telephony.cts.TelephonyManagerTest#testGetNetworkSlicingConfiguration: PASSED (2ms)

Change-Id: Ia02d92b28a7bb8c8e171ce05177debed045a1570
2 files changed