Consider to stop using the CSS class button-link for controls that don't look like links

[afercia]

After [40059] the CSS class button-link uses text-align: left by default. This makes sense, since this class should be used to make buttons look like links. Browsers default stylesheets make text within buttons centered, so there's the need to make the text explicitly left aligned to prevent some edge cases, see for example #38712.

However, now the media modal "X" close button text is misplaced. Worth checking if the same thing happens for other buttons too. In these cases, text should be centered:

It's a minor visual glitch and can be easily fixed. Ideally, these buttons shouldn't use the button-link class at all. They'd need just some reset of the default buttons CSS properties.

[afercia]

39983.diff​ removes the button-link CSS class from the media modal close button and adjusts the styles accordingly. Pending investigation about other edge cases.

[afercia]

39983.2.diff​ adds a few adjustments for the button text alignment in the Customizer and in the auth-check modal.

[swissspidy]

Patch works as expected.

[afercia]

In 40358:

Administration: Fix minor misalignments caused by the button-link CSS class.

After [40059] the CSS class button-link uses text-align: left by default.
This change now requires to limit as much as possible the use of button-link
to controls that should really look like links and to explicitly set
text-align: center in a few other cases.

Fixes #39983.

[afercia]

Re-opening for 4.7.4 consideration.

[swissspidy]

In 40367:

Administration: Fix minor misalignments caused by the button-link CSS class.

After [40059] the CSS class button-link uses text-align: left by default.
This change now requires to limit as much as possible the use of button-link
to controls that should really look like links and to explicitly set
text-align: center in a few other cases.

Fixes #39983.

Merges [40358] to the 4.7 branch.