R1:6e4f508bebdb

Provide "builtin" high-level result orders

Summary:
Ref T7803. Currently, available high-level orders are spread across Query and SearchEngine classes and implemented separately for each application.

Lift the concept of "builtin" (high-level, user-facing, named) orders (similar to "builtin" queries in ApplicationSearch) into the root Query class, and let it drive the SearchEngine implementation. This allows you to define a new order in one place and have it automatically work across the entire stack.