R1:46695c76ebfe

Introduce "DiffusionCommitGraphView", which unifies "HistoryListView" and "HistoryTableView"

Summary:
Ref T13552. Currently, commit lists are sometimes rendered as an object list and sometimes rendered as a table. There are two separate views for table rendering.

Add a fourth view ("list, with a graph") with the eventual intent of unifying all the other views. For now, this only replaces "HistoryListView" -- and needs some more work to really be a convincing replacement.

Test Plan:
- Looked at…