Tweak ContextHub HAL 1.2 based on feedback

To assist in making permissions attribution more robust at the
ContextHub service level, tweak the V1.2 interface with the following
changes:
- Return the full list of supported permissions that all hubs support
for attribution. This assists in limiting the number of permissions
strings sent between the HAL and service to only those the HAL actually
attempts to use.
- Add new parameter to handleClientMsg_1_2 that allows nanoapps to
denote the list of attributable permissions relating to the contents of
the message being sent. This is strictly a subset of the permissions the
nanoapp holds and allows a message to be sent without attributing the
full nanoapp permission set to the host client when the message may not
have been generated from data covered by the permissions.

Bug: 166846988
Test: compile
Change-Id: I2dc8e1ab4fce2a9ebcc393d07fdffe23dfceb4c2

contexthub/1.2/IContexthub.hal

@@ -16,12 +16,24 @@
 
 package android.hardware.contexthub@1.2;
 
+import @1.0::ContextHub;
 import @1.0::Result;
 import @1.1::IContexthub;
 import @1.1::SettingValue;
 import IContexthubCallback;
 
 interface IContexthub extends @1.1::IContexthub {
+    /**
+     * Enumerate all available context hubs on the system.
+     *
+     * @return hubs                 list of hubs on this system.
+     * @return supportedPermissions list of Android permissions all hubs
+     *                              support for nanoapps to enforce host
+     *                              endpoints are granted in order to
+     *                              communicate with them.
+     */
+    getHubs_1_2() generates (vec<ContextHub> hubs, vec<string> supportedPermissions);
+
     /**
      * Register a callback for the HAL implementation to send asynchronous
      * messages to the service from a context hub. There can be a maximum of

contexthub/1.2/IContexthubCallback.hal

@@ -24,10 +24,18 @@ interface IContexthubCallback extends @1.0::IContexthubCallback {
      * implementation to allow the HAL to send asynchronous messages back
      * to the service and registered clients of the ContextHub service.
      *
-     * @param msg message that should be delivered to host app clients
-     *
+     * @param msg             message that should be delivered to host app
+     *                        clients
+     * @param msgContentPerms list of Android permissions that cover the
+     *                        contents of the message being sent from the app.
+     *                        This is different from the permissions stored
+     *                        inside of ContextHubMsg in that these must be a
+     *                        subset of those permissions and are meant to
+     *                        assist in properly attributing the message
+     *                        contents when delivering to a ContextHub service
+     *                        client.
      */
-    handleClientMsg_1_2(ContextHubMsg msg);
+    handleClientMsg_1_2(ContextHubMsg msg, vec<string> msgContentPerms);
 
     /**
      * This callback is passed by the Contexthub service to the HAL