New BillingCycleRepository

Migrate BillingCyclePreference to BillingCycleRepository first, will
also migrate DataUsageList in future cl.

Also fix an issue that the BillingCyclePreference initial enable state
not set.

Bug: 290856342
Test: manual - on mobile settings
Test: unit test
Change-Id: Idd171fefbc30763010afb7bfb68543612f7b9b1a