Add helper functions for emergency device configs.

Added helper functions to check two new demergency number database
related device configs. The first new device configs returns a boolean
representing whether modem/config sourced emergency numbers should be
ignored. The second new device config returns a boolean representing
whether emergency number routing defined in the android emergency number
database should be ignored.

Bug: 247636518
Test: manual
Change-Id: I1398f36070799a7b9c8c01ec084853cb26bf610b