The property squashing functions were performing 19% of all allocations
and allocating 3.43 GB, most of which was used to track the name of the
property, but the name of the property is only used to print errors.
Keep the elements of the name in a preallocated slice instead, and only
compute the name when an error occurs.
Calling reflect.Value.Interface() was also expensive, and only passed
to filter and order functions, none of which use the values. Modify
the signature of the filter and order functions to remove the interfaces
and the property name.
Test: extend_test.go
Change-Id: I517f89daf251bb43f7cfefa6f1e83951c0e271b7
c4fc4b447f