Check user data enabled on phone and add listener

Check phone#isUserDataEnabled() before trying to set it as preferred
data phone. PhoneSwitch now also listens to data enable change, and
re-evaluate DDS when events are received.

Bug: 126769655
Test: Build
Change-Id: I599bea363f24a3de0e102c2e32cad132dcc0bbec
Merged-In: I599bea363f24a3de0e102c2e32cad132dcc0bbec
(cherry picked from commit 86d02753)