Add Emergency Number metrics for Q

- define Emergency number proto
- log updated emergency number when it's reported in EmergencyNumberTracker
- log emergency number info when CS call ends
- log emergency number info when IMS call ends
- apply RNG per country population percentage to collect emergency call
metrics in ~250 countries

Test: Treehugger
Bug: 129562296
Bug: 132454968
Change-Id: I08bf4d2172691c221f89e3139d1e99929d8c83b7