Moves IMS Emergency Calling availability out

Moves the IMS Emergency Calling availability
state out of ImsServiceController and into
MmTelFeatureConnection. This allows the ImsResolver
to treat FEATURE_EMERGENCY_MMTEL as a feature,
like the other FEATUREs, and push updates to
FEATURE_EMERGENCY_MMTEL to the MmTelFeatureConnection
instead of polling it.

Bug: 74389647
Test: Telephony Unit Tests, Telephony ImsService Testapp
Change-Id: I0e7b1ffb8b1e82e447096c8cc74d7f825c945798