Support Dynamic ImsService Querying

1) Provide a "default" impl for MmTelFeature
instead of returning null.

2) Introduce a FeatureSlotPair, which maps a SIM
slot ID to a ImsFeature. This allows the ImsService
to provide which features it supports for multi-SIM
phones.

3) Pipe through ImsResolver state to help prevent IMS
operation when the ImsResolver is in the process of
figuring out feature capabilities.

Test: Telephony ImsService test app, telephony unit tests
Bug: 72642524

Merged-In: I4d7e9ba630739ade83e3242488f330ea6e73bbd7
Change-Id: Idb95f7651af200026d62e8b29eaed30bc0ebc9d3