[SM13] Create new atom for reporting data usage per rat and per sub

Currently, modify MobileBytesTransfer(ByFgBg) to add dimension
for rat type and subscription is not backward compatible since
callers might expect a complete statistics in a metrics with
specific uid.

Hence, create a new atom to report data usage per rat and per
subscription.

Test: build
Bug: 148905838
Bug: 129082217

Change-Id: Id1c8673d92038552c2393b017f5723fd5c79ab45