Refactor js/entity_browser.modal.js to use core/once

This might be a nice novice task to learn JS refactoring to core/once and implementing tests.

Attached patch replaces the processed class pattern with core/once API as requested.

Changes made:
- Replaced hasClass/addClass('entity-browser-processed') with once() API in entityBrowserModal behavior
- Added 'once' as function parameter following the same pattern as entity_browser.tabs.js
- entity_browser.tabs.js was already correctly using once() - no changes needed

Testing completed:
- All entity browser modals open and function correctly
- Entity selection works properly
- No JavaScript console errors

Ready for review.

@miroslavstankov please use the MR, not patches.

Thanks for the feedback. I’ve created MR !102 to replace the patch, as requested. Ready for review.

anybody → changed the visibility of the branch 3542178-refactor-jsentitybrowser.modal.js-to-core-once to hidden.

Renamed $button to $inputs and button to inputElement for clarity