Use semantic HTML for buttons in Django Admin

[Eliana Rosselli]

Right now the Django Admin has some buttons that are actually link tags with role="button" set, i.e

<a role="button">

We also have anchor elements with

<a href="#" >

that are also acting as buttons. One example is the "Today" button that can be found next to date and time inputs.

We should change these to be proper HTML buttons , and update their CSS so they maintain their existing styling. Below is an example of this kind of button; in the image, the "Add another Release" button is using an anchor element

[Eliana Rosselli]

Example of a button that uses an anchor tag: "Add another Release"

[Sarah Boyce]

This is a follow on from #35795

[Thibaud Colas]

I see at least two separate issues here:

1. There are a elements with JS behavior added where the role="button" is an improvement but we can go further, and we would be better off with <button>.
2. There are a elements that don’t have any JS behavior added, and the role="button" isn’t appropriate. They shouldn’t have a role as they are links that take users to a separate page.

The admin’s styles are very similar for both types, but we need separate elements.

I believe PR #19283 only tackles the first point for now.

[Thibaud Colas]

I’ve assigned the second point to @kushaldas as this seems different enough from the improvements in ​PR #19283 (that PR is improvements over existing, while point 2 would be considered a bug I think)