Always show disabled pSIMs in single-sim mode

In single-sim mode, you can have both an eSIM subscription and a pSIM
inserted into the device, and only one of them can be enabled. It turns
out that if the pSIM is the disabled one, we would not show it in the
settings UI; this CL fixes that.

It also fixes a somewhat related problem that I noticed while testing
this, that if you have only one subscription that happens to be
disabled, we were not showing the on/off switch at the top of the page,
which would leave you with no way to enable it.

Bug: 129864878
Test: make RunSettingsRoboTests
Change-Id: I4214ad34c59ac2df429772c066c51a9318f5baa7