Accessibility: Administration: Underline links on Dashboard that are located...

Accessibility: Administration: Underline links on Dashboard that are located within a line of text and thus need to be underlined:

* "change your theme completely"
* Active theme in the "At a Glance" box
* "View all drafts" in the Quick Draft box

Split "Manage widgets or menus" into separate items for consistency with other links.

For better accessibility, links that are a part of other text should be underlined and not rely on color alone to be distinguished.

Per accessibility coding standards:
> When links can be identified as such by the context, for example because they’re part of a menu, or a set of links clearly identified as user interface controls, they don’t necessarily need to be underlined. In all the other cases, especially for links surrounded by other text (in a line or block of text), links need to be always underlined.
https://make.wordpress.org/core/handbook/best-practices/coding-standards/accessibility-coding-standards/#links-underline-or-no-underline
https://make.wordpress.org/accessibility/handbook/design/use-of-color/#not-by-color-alone

Props afercia, audrasjb, karmatosed.
Fixes #48406.
Built from https://develop.svn.wordpress.org/trunk@46770


git-svn-id: https://core.svn.wordpress.org/trunk@46570 1a063a9b-81f0-0310-95a4-ce76da25c4cd