Import 51870.2.diff and adjust some instances.

[kebbet]

Improvements from 51870.2.diff.

Updated:

• image-editor .imgedit-settings .imgedit-help-toggle:focus
• functions.php with focus styles (and new link colors)
• #screen-meta-links .show-settings:focus was missing the change to border-color.

https://core.trac.wordpress.org/ticket/51870

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