Functionality and design problems with widgets accessibility mode

[shaunandrews]

Recent updates to the widgets page break the ability to add new widgets in accessibility mode, and the edit link doesn't fit the current style.

[shaunandrews]

Accessibility mode's edit link doesn't overflows the widget and has a border-radius set.

[shaunandrews]

Making accessibility mode work again.

[shaunandrews]

In 26165.diff​

• Hiding/Showing the relevant edit/add links for widgets in available widgets, inactive sidebars, and sidebars.
• Removing the now-defunct gear icon.
• Keep the border-color of widget-top the same, and no pointer cursor when hovering.
• Showing the widget-inside when editing/adding a widget.
• Show all widgets and sidebar descriptions for closed sidebars.

(The above all applies only to accessibility mode.)

[azaozz]

In 26439:

Widgets: fix no-js and accessibility modes, props shaunandrews, fixes #26165.