Modified merging of duplicate emergency numbers

Changed merging logic in combined list of DB and radio list.
Service category and urns are not compared to check duplicate.
It is set from one of the duplicate number based on its source as per
the precedence of Network/SIM/DB/modem_cfg.

Test: atest EmergencyNumberTest & EC in device
Bug: 238359415
Change-Id: Icf5686f5b0ea8d3bc29d6c0fbe7be3ef05ccc65c