The eLearning area has been adjusted to better organize how slide and course upload features are loaded and managed. This should make the course content upload experience easier to maintain and support future improvements with minimal user-facing disruption.

The search panel category default selection logic was reorganized into a dedicated internal function. This does not change the user experience directly, but it makes the web interface easier to extend and maintain for future features.

This commit extracts the logic of the selection of the default
value for search panel categories into a private function
so it can be hooked in other modules.

task: #1959112