Remove on/off toggle for physical SIMs

Our original design for mobile network subscription management included
having an on/off toggle for both eSIMs and physical SIMs. However, it
turns out that our current telephony stack has some problems with
disabling physical SIMs, so for now we're removing the on/off
toggle. Because of this, we've added a footer to the SIM details page
for physical SIMS letting users know that to disable them you need to
remove them from the device.

Even though we're removing the on/off toggle for pSIMs, there are still
a few edge cases where you could end up with a disabled one (eg having
two SIMs in single-SIM mode where the eSIM is active and then you erased
the eSIM). In order to have a way to re-enable the pSIM in these cases,
this CL changes the relevant pref's summary to "Tap to activate <name>"
and makes the tap action begin the re-enabling. This can affect either
the Mobile network pref on the Network & internet main page (if this
disabled pSIM is the only SIM), or an entry in the Mobile networks list
page (if there are still multiple SIMs present).

Finally, this also fixes a problem where we weren't showing the on/off
toggle for eSIMs if you only had one SIM total; we actually always want
to show it for eSIMs.

Bug: 132921553
Test: make RunSettingsRoboTests
Change-Id: Id0750ebd5bed46dc2450b65b53cc81847ef09b82