R1:2b0632b442a2

Remove "DiffusionHistoryTableView" and "DiffusionHistoryView"

Summary:
Ref T13552.

Currently, the "Browse" page shows a snippet of unmerged changes if you're looking at a non-default branch. Remove this for consistency with the simplified main "Browse" page. This is reachable via "Compare".

Update the "Compare" page to use the new "CommitGraphView".

Test Plan:
- Looked at the "Browse" page of "stable".
- Looked at the "Compare" page for "stable vs master".

Maniphest Tasks: T13552

Differential…