In wp_image_editor(), use wp_image_editor_supports() to check for rotation...

In wp_image_editor(), use wp_image_editor_supports() to check for rotation capabilities rather than directly checking the existence of the imagerotate function.

In WP_Image_Editor_GD::test(), check for existence of imagerotate if the rotate capability is required.

Props DH-Shredder
fixes #22597


git-svn-id: https://core.svn.wordpress.org/trunk@22863 1a063a9b-81f0-0310-95a4-ce76da25c4cd