Rework V1.2 ContextHub HAL spec

In the final implementation that makes use of this HAL version,
ContextHubMsg's don't have permissions information when they are sent
from the framework to the HAL since the framework is the end decider for
whether its clients have the right permissions.

Bug: 180606685
Test: presubmits
Change-Id: I385edce48ff71abc1c684919532b6c578df2a414