Support Dual ViLTE stats

Some operator supports multiple VILTE,
both two SIM cards can make VILTE call.
We need to record VILTE data to different interface.
Now NetworkStatsService has only one VILTE data
interface: "vt_data0". All VILTE data stats will
be recorded in this interface.

Bug: 130871087
Test: NetworkStatsServiceTest#testDualVilteProviderStats
Change-Id: I1248b78e628bdf1f6b7bee360bdaecd283799c8e