Move filterMobileSubscriptionInSameGroup into KeyguardUpdateMonitor.

This avoids race condition that, KeyguardUpdateMonitor refreshes active
sub list however CarrierTextController filtered it based on stale active
data subId.

By move filterMobileSubscriptionInSameGroup into KeyguardUpdateMonitor,
it becomes the single source of truth about which carrier name should be
shown.

Bug: 138456731
Test: manual and unittest
Change-Id: Ida3a90c5408b056cad7a79fbba84fe880ce1e5be
6 files changed