[Telephony Mainline] Use new method for mainline

- TelephonyBackupAgent.getActiveSubscriptionInfoList(boolean)
    -> getActiveAndHiddenSubscriptionInfoList()

- TelephonyProvider
    - TelephonyManager.from -> getSystemService
    - TelephonyManager.getSimOperator(int) -> getSimOperator()

Bug: 144972924
Test: make & atest TelephonyProviderTest/TelephonyBackupAgentTest
Change-Id: I9998906fa258632bb4e780fae80aa5bf89d28226
3 files changed