Revert "Revert "Listen for individual subscription mobile data toggles""

This reverts commit f598641d.

Reason for revert: Build breakage could not possibly have been th caused by the initial CL. Cause was a String index overflow "Caused by: com.android.tools.r8.internal.du: String-index overflow."

Tested with local build of aosp-master/full-eng, completes successfully.
Change-Id: I207372c9513b450cf246874ba1d1e98dbd147f27