Add interface to get the value loaded from ISIM record

This CL modifies the interfaces to allow the IMS service to get the value loaded from the ISIM record.
1. Allow access to the interface to privileged apps by adding @SystemApi annotation.
2. Add interface to get P-CSCF from the ISIM record instead of getIsimPcscf.
3. Add interface to get SIM Service Table that return byte array type.

Bug: 365488868
Test: atest TelephonyManagerTest
Flag: com.android.internal.telephony.flags.support_isim_record
Change-Id: I6db5ffa73337bc1448726db72ca30e85bf6d07d8