Fix 'Advanced' collapse point on Network & internet page

On the Network & internet page, we want to collapse all the prefs into
'Advanced' that appear after 'Data Saver'. The mechanism for specifying
where the collapse point starts is just a static count, and it doesn't
really understand the concept of dynamically added preferences like the
ones we add at the top when the device is in DSDS mode. To fix this in
the short term, this CL makes the header that manages these prefs
manually adjust the count as needed. In the future we'd like to have a
better mechanism for this added in the support library.

Fixes: 128855968
Test: make RunSettingsRoboTests
Change-Id: I4509726ff29bc71e1f0b3d4a2f60dffe4b1dd7ac