Changeset 38710 for trunk/tests/phpunit/data/themedir1/camelCase/index.php

Themes: Account for uppercase chars when managing themes.

Fixes a bug where the UI wasn't updated after deleting/updating a theme.

Also introduces unit tests for theme management ajax handlers. For now they're
focused on wp_ajax_update_theme() but they can include tests for other
handlers as well.

Props chrisjean for initial patch.
Fixes #37924.