Use helper method for determining whether eSIM is supported

It turns out to be more complicated than I had thought to determine if a
device should be considered to support eSIM. But the good news is that
we already had a helper method for this - this CL switches to using it
in some code for DSDS UI.

Fixes: 129061243
Test: make RunSettingsRoboTests
Change-Id: I41e500eb70b6c6b725c0ddf09fe1ca1a69df4563