Reland: Add getprop to toolbox

Add a non-toybox version of getprop, so that we can interface with the
new C++ PropertyInfoAreaFile class to return property context
information.

Bug: 36001741
Test: Compared toolbox getprop results with toybox getprop
Change-Id: I4e90aa5b843cb5cfcbe85f05f23ae8e22729b26e