R1:c0bec6c0ed81

Add "parent" and "ancestor" information to the project.search API

Summary:
Ref T12074.

- Adds a new "parent" property on main results. This shows an abbreviated version of the project's parent, or `null` if the project is a root project.
- Adds a new "ancestor" attachment to pull the entire ancestor list.
- Adds a new "depth" property on main results.
- You can use "parent" or "depth" to tell if a project is a subproject or not.

These attempt to balance convenience, power, and performance: the…