R1:35df988036f7

Use standard UI elements to render pull requests in Releeph

Summary:
Ref T3718. Ref T3644. Ref T3092. Switches from the Releeph UI elements to standard ones. I'll attach some screenshots.

Also fixes CSRF against the request action endpoint.

Test Plan:
- Viewed request details.
- Took actions on a request from detail page.
- Viewed request list.
- Took actions on a request from list page.
- Used keyboard shortcuts to navigate list.
- Used keyboard shortcuts to take actions.
- Simulated…