R1:3068639ccffc

Implement query and policy rules for subprojects

Summary:
Ref T10010. This implements technical groundwork for subprojects. Specifically, it implements policy rules like Phriction:

- to see a project, you must be able to see all of its parents (and the project itself).
- you can edit a project if you can edit any of its parents (or the project itself).

To facilitiate this, we load all project ancestors when querying projects so we can do the view/edit checks.

This does NOT yet implement…