Convert file_icon_class() and file_icon_map() to a utlity class and deprecate

Applied the MR and searched for file_icon_class + file_icon_class and only one instance of each which was deprecated.

Tests are added to show deprecation, https://git.drupalcode.org/issue/drupal-3411266/-/jobs/544804

LGTM

I moved the cspell:ignore line. It should be before the class declaration and after any use statements. I used the Web IDE an had the pleasure of making the change twice. :-)

Leaving at RTBC.

Wondered if it was worth making this extensible or swappable but I searched the issue queue and found no issues discussing either of these, so I think this is fine just to move to a static utility class, especially given each method only has exactly one usage in core.

Committed c936bda and pushed to 11.x. Thanks!

longwave → closed merge request !5974

Automatically closed - issue fixed for 2 weeks with no activity.