Add placeholder properties for emulator

Add some placeholder properties in google VHAL. Developers who use the
aae emulator can use them in developing new features without
implementing a real property.

Bug: 193460353
Test: build aae emulator, use adb lshal to change property values
Change-Id: I6131a4892495c4c1e1c73e078572a666a33f984e
Merged-In: I6131a4892495c4c1e1c73e078572a666a33f984e
(cherry picked from commit 4d1fe81b)