R1:90d0f8ac6cf5

Revert changes to Diffusion blame view

Summary:
Ref PHI174. This reverts most of these changes:

- 37843127e94a878a7f5bf2c65c8e7004bc65c68a / D18481
- 94cad30ac3f052a711ececf7e370bf5c0071827f / D18474
- 12ae08b6b1a1b7c330593e76c32817f7cdbc87dd / D18473
- 0a013341721f8b1fc249047fe6db26062138b562 / D18462
- ac91ab1ef9196eee0deabfd70157ccc0d53d666e / D18452

These changes made the Diffusion blame view very similar to GitHub's blame view. See D18452 for a before/after of the bulk of these changes; the other…