Add support for ApnSetting.TYPE_OEM_PAID and OEM_PRIVATE

This change adds a flag oem_paid_private

Bug: 366194627
Test: m
Test: manually add oem_paid APN to telephony.db and verify OEM_PAID
      network capability in adb shell dumpsys connectivity
Flag: com.android.internal.telephony.flags.oem_paid_private
Change-Id: Ibc29e7a49c968eca52f3f4a24b13e854f376245d