Update isEmergencyNumber() feature flag dependency

Given that isEmergencyNumber() functionality is utilized by both calling
and
messaging modules, and messaging can be enabled without calling, the
function's access control should be based on FEATURE_TELEPHONY_CALLING
or FEATURE_TELEPHONY_MESSAGING.

Bug: 395178686
Flag: EXEMPT bug fix
Test: atest CtsTelephonyTestCases --no-bazel-mode
Change-Id: I7967ce12e817a35e7b5f57058232bc100bd16023