Fix tab sequence order in the Media attachment browser

[afercia]

In the media views attachments browser, the visual order of the Close, Previous, and Next buttons doesn't match the DOM order.

For accessibility, visual order and DOM order must match when this affects the meaning and operability of a page.

Success Criterion 2.4.3 Focus Order
​https://www.w3.org/TR/WCAG21/#focus-order

If a Web page can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components receive focus in an order that preserves meaning and operability.

Making visual and DOM order match benefits keyboard users who navigate documents sequentially and expect the focus order to be consistent with the sequential reading order.

Affects, for example:

• keyboard users, whether they just prefer to use a keyboard or must rely on keyboard
• users with disabilities that make reading difficult
• users with visual impairments
• screen magnifier users

[afercia]

Wrong DOM order in the attachments brower

[afercia]

Problem :

• the Close button comes from the media modal template thus the CLose button is first in the DOM order
• then, the edit-attachments view adds the Previous and Next buttons: they're after in the DOM source and absolutely positioned to make them appear before the Close button
• these elements can't be rearranged because they pertain to different views

47458.diff​:

• makes the modal Close button optional via a hasCloseButton property, default: true
• makes the edit-attachments template use its own Close button so it can be placed in the right order
• no visual changes

[afercia]

47458.2.diff​ refreshes the patch. Also, resets all the attributes inherited from the Attachment view, including tabindex=0, data-id, etc. that are inappropriate on the attachment details <div>. See [30483] / #30390.

[afercia]

In 45506:

Accessibility: Fix the order of the Previous, Next, and Close buttons in the Attachment Details modal.

Making the visual and DOM order match benefits keyboard users who navigate documents sequentially and expect the focus order to be consistent with the sequential reading order.

Fixes #47458.

[joemcgill]

Reopening this so it can be back-ported to the 5.2 branch.

[audrasjb]

Adding needs-testing keyword to validate if this ticket is good to land in 5.2.3 (should be ok though).

[audrasjb]

Tested on my side against 5.2.2, but unless I'm mistaken [45506] doesn't look to apply cleanly: trunk/src/wp-includes/media-template.php seems to have some dependancies to previous commits.

Could you check on your side @afercia?

[SergeyBiryukov]

In 45849:

Accessibility: Fix the order of the Previous, Next, and Close buttons in the Attachment Details modal.

Making the visual and DOM order match benefits keyboard users who navigate documents sequentially and expect the focus order to be consistent with the sequential reading order.

Props afercia.
Merges [45506] to the 5.2 branch.
Fixes #47458.