[Wi-Fi] Fix multi SIM devices switch to mobile data automatically settings missing problem

Context#getResources loading is done based on the last SIM to
come up, we may get wrong customization settings.

This fix check the setting of active subscription and shows the preference.

Bug: 138956509
Test: CellularFallbackPreferenceControllerTest
      manual test:
          1. Insert feature supported SIM and check UI.
          2. Remove feature supported SIM and check UI.
          3. Turn airplane mode on and check 1. and 2..

Change-Id: I72b6db415429181395a02f163889bb1b9c0f070f
Merged-In: I72b6db415429181395a02f163889bb1b9c0f070f