Added fake VHAL value generator based on JSON file

Note: It only supports a single generation task at any time. Mixed value
properties like diagnostics frame is not implemented yet. It only
supports properties with ON_CHANGE mode for now.

Bug: 76017041
Test: lunch bat_land-userdebug & m -j8; adb push <json_data>
/data/local/tmp; use python emulator to inject fake value "start" command
specifying the JSON data path on device; verify values on KitchenSink app

Change-Id: Ic964ef52a19422bab7015fe54c7e4c5ef8b47a55