Define Wifi Offload HAL HIDL interface

This interface defines the interaction of the Wifi framework with the
new HAL module that will offload disconnected PNO scans when screen is
off. For details of the overall design, refer to this document:
https://docs.google.com/a/google.com/document/d/13OmqquTnRXTRnyWbtfpc1Ib7YY411EwjNW3njzJ5KyM/edit?usp=sharing
Cherry pick from 7ac4a32e6eca71fcf1a86991654af747d38928ad
Bug: 32842314
Change-Id: I01e1952458d58b9233f18fc0450491fc7c48e6e1
Test: Unit tests, Mannual Wifi turn on