[FIX] web: basic_renderer: delay destroy after render when rerendering widget

Steps to follow

  Edit the account.move view (with studio for example)
  Set the lines readonly property to [["partner_id","=",False]]
  Create a new move
  Add a partner
  Add a product
  Remove the partner
  -> A traceback appears: widget.$el is undefined

Cause of the issue

  widget.$el is used after the widget has been destroyed

This commit corrects it, by waiting for new widgets to be "mounted" before destroying
old ones. The code already exists in 14.0 (3fd7b200).

opw-2557142

closes odoo/odoo#78625

Signed-off-by: Lucas Perais (lpe) <lpe@odoo.com>