Add power properties

Refactor handling of property specific code in emulator.  The
AP_POWER_STATE property is different from other properties in the system
because it has different values for get/set.  Thus, it needs to be
special cased by the default emulator.

Bug: 32061842
Test: VHAL emulator
Change-Id: Ic325ef401abbcf09a7808a9eca01cbfe8b3cc94f