[DU07]Remove BatteryStatsImpl NetworkStats.subtract dependences

BatteryStatsImpl is using INetworkStatsService APIs, which
cannot be accessed after moving into the mainline module. So, replace
and remove those hidden API usages.

Bug: 213523117
Test: atest BatteryStatsImplTest WifiPowerCalculatorTest
            MobileRadioPowerCalculatorTest
Change-Id: I9e8d94259ad9845d94bfd78d971ff1a2cd7bb38e