[FIX] web_editor: prevent a modal from closing when dropping a snippet

Before this commit, when you dropped a snippet using the move button
in a modal. The modal closed after the drop.

This commit allows to define an element in which to destroy the
editors.

Part of https://github.com/odoo/odoo/pull/61998


task-2312878

closes odoo/odoo#61998

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>