Adding API for defining and invoking DirectActions

DirectActions are abstract actions defined by an Activtiy. The
actual definition of these actions will be available through
the support lib.

This API provides a secure channel for system or assistant to
interact with a running app using these Actions.

Test: atest CtsVoiceInteractionTestCases
Test: added android.voiceinteraction.cts.DirectActionsTest

Bug: 129705716

Exempt-From-Owner-Approval: Resolving merge conflict

Change-Id: I0ce568e0d8f41e0fe46306052016a74c7b394efa
(cherry picked from commit d40c3455)