Drop jQuery dependency. Convert to vanilla JS

IS: Referring to a file that needs to be deleted

I believe we should first attempt to limit the amount of code.
https://www.drupal.org/project/private_message/issues/3487705 📌 Refactor BanUserForm Active
https://www.drupal.org/project/private_message/issues/3487692 📌 Refactor private_message_thread_member_widget Active
https://www.drupal.org/project/private_message/issues/3487689 📌 Drop uninstall_page library Active

Some parts are undergoing frequent updates, which may generate conflicts and unnecessary work.

Some of the tickets were approved & merged. 📌 Refactor private_message_thread_member_widget Active is still in progress, it seems

Postponing on 📌 Full coverage for JS/Ajax functionality Active