[Sat] Fix check for all mobile connections OOS

`areAllConnectionsOutOfService` is a StateFlow that chose `false` as its
initial value. This is incorrect, because the value should be `true`
until the `MobileIconsInteractor` yields a list containing at least one
non-OOS subscription.

Also update the tests to use better flag practices

Bug: 322203863
Test: DeviceBasedSatelliteInteractorTest
Flag: ACONFIG com.android.internal.telephony.flags.oem_enabled_satellite_flag DEVELOPMENT
Change-Id: I0f6eafdb3e7f58728da88b8eb6ee294a0a771366