Port DiffViewerPage and DiffViewerPageView to spina.
Review Request #12940 — Created April 5, 2023 and submitted — Latest diff uploaded
This change ports the diffviewer page model and view to spina. These
files have been moved into thereviewssubdirectory to correspond to
the bundle they're a part of.
- Ran js-tests.
- Tested the diffviewer page.