We show a list of commits in the review request info box, the change

description boxes, the diff viewer for normal diffs, and the diff viewer

for interdiffs.
Each of these were essentially a different take on the commits list. We

three templates (2 as Django templates, 1 in JavaScript), and they were

not consistent. They didn't all agree on the same class names or

structure.
Many of the CSS class names used either piggy-backed on other styles or

conflicted with them. Some of those were deeply-scoped class names, and

some were just accidentally referencing other classes.
This broke recently with some of the work for fixing up the review

request layout and field definitions. Rather than trying to make another

attempt at reconciling all the templates and working around CSS classes,

this change fixes this up for good.
We now have a single documented CSS component for the commits list,

carefully structuring namespaced CSS classes covering all our commits

list uses.
The two Django templates have been merged into one. That means we now

have only one Django template, one JavaScript template to maintain. This

is still one more template than I'd like, but it does simplify things,

and both use the new namespaced classes to avoid future issues.
Some behavioral changes with the old list have been fixed. We no longer

maintain our wonky, non-accessible expand/collapse logic. Instead, we

use a <details> tag, which gives us exactly what we want and allows

screen readers to grab the summary and the commit description

separately. This looks, feels, and styles better than what we had

before.
We also have the ID column once again. The original commits list had

this, but it was removed for some reason, and that made this list far

less useful for reconciling commits. It's been brought back, and shows

the ID in a shortened form, with the full ID shown in a tooltip.
Ultimately, this deletes more code than it adds, simplifies all the

current logic, makes it easier to reason about, and removes all style

conflicts.

Tested every scenario that the commits list appears in, with all possible

states, to be absolutely sure there are no style issues or regressions.
Tested at various browser widths. There's more work to do for mobile, but

not for 6.0. It's better now than it was.
Tested the columns with large amounts of data, making sure they truncate

correctly.
Tested expanding and collapsing, and tested with commits with and without

a commit body.
Tested the accessibility tree. It's not perfect, but is better than before.
All Python and JavaScript unit tests pass.