Adjust theme details buttons to improve proximity of controls

[joedolson]

Related: #40822

​https://cldup.com/bzuc02OcHD.jpg

The theme modal at Appearance > Themes places the 'Delete' button remotely from other theme buttons. For improved accessibility, the three buttons should be grouped together.

Should also switch order of buttons so the Primary action is first: Live Preview / Activate / Delete.

[joedolson]

Screenshot with patch

[joedolson]

Update order of buttons & center.

[joedolson]

While looking into this, I also observed that the color of the delete link failed color contrast at 4.4:1, so this patch also adjusts the color to the next darker red shade.

To test: verify that buttons are in the new order and orientation.

[joedolson]

Logistically, this will be more sensible to commit simultaneously with #59372; test this using the patch on that ticket.

[joedolson]

In 56639:

Administration: Improve control proximity in theme details modal.

Make the theme details modals in the Customizer and at Appearance > Themes consistent. Change the order of controls so both modals are in the same sequence, center all controls in both desktop and mobile views, and change delete link color to meet color contrast requirements.

Props trishasalas, afercia, melchoyce, karmatosed, cathibosco1, michaelarestad, joedolson, petitphp, mikinc860.
Fixes #59372. See #59371, #40822.