Ensure all Style dependancies are set

[dd32]

This is a follow on to #26236

We need to ensure that all styles have their proper dependancies set prior to release, if something needs dashicons, it should be set as a dependancy, etc.

For dashicons specifically, here's a one-liner to list the files that refer to 'dashicons': (I'm sure it can be simplified)
find ./ -iname *.css | grep -v 'wp-content/' | sed "s/.\///" | xargs grep dashicons | sed "s/:.*$//g" | uniq

Attached is a patch that adds the dashicons dependancy to the remaining files, however, we should leave this ticket open and revisit at RC time.

[nacin]

In 26596:

Declare dashicons dependency for wp-pointer.css and media-views.css.

props dd32.
see #26255.

[nacin]

In 26605:

Add Open Sans as a dependency to install.css and add Dashicons as a dependency to some other CSS files. see #26255.

[nacin]

I went by these guidelines:

• Dashicons needs to be a dependency everywhere it is used.
• Open Sans does *not* need to be a dependency everywhere.

Basically, Open Sans is for the admin. The toolbar, the installer screens, and the admin all need it. But I'm not sure using the media manager on the frontend requires Open Sans to work. (Of course, if Open Sans was installed on the computer, it'd load.)