R1:2712091a7148

Move Releeph branch controllers toward a modern/stable state

Summary:
Ref T3644. Ref T3657. Ref T3549. Basically:

- Move these controllers to modern query/policy infrastructure.
- Move them to consistent, ID-based URIs.
- Rename "Project" to "Product"; "Pick Request" to "Pull Request".
- Clean up a few UI things here and there.

Test Plan:
- Created and edited branches.
- Opened and closed branches.
- Viewed branch history.
- Searched within a branch.
- Browsed to branches from products.