[RTT2] System API for a Responder Configuration

The Responder Configuration is an abstracted specification of the peer
RTT Responder (to which we initiate an RTT operation).

The Responder is abstracted from a ScanResult (for an AP) or a Wi-Fi
Aware PeerHandle or MAC address. Utility methods are provided.

The Responder configuration is the underlying representation used by
the RTT manager and service to communicate infomration on RTT targets.
This API thus does not provide any additional permission or backdoor
hooks to the RTT functionality. It exposes a lower level utility
representation of the data. We may choose to make this more widely
available in the future if necessary.

Bug: 65108607
Test: builds
Change-Id: I620d8e725ad61792b7604ff1355adb1b0ef38ad1