Before this commit, the sub-menus that appear when the mouse hovers them
were not displayed correctly. The public widget which is in charge of
positioning the sub-menu (`menuDirection`) could not work because the
dropdowns were opened manually (which is not recommended) and so, the
`show.bs.dropdown` event was never triggered which prevented the public
widget from aligning the sub-menu items correctly.

Steps to reproduce the bug:
- Have a long sub-menu in the last position of the navbar.
- In edit mode align the navbar elements to the right.
- Enable the option to have the sub-menus displayed at hover.
- Save the page.

=> When hovering the sub-menu, it opens on the right and overflows the
page while there is enough space on the left.

task-2904507

closes odoo/odoo#115153

Signed-off-by: Bojabza Soukéina (sobo) <sobo@odoo.com>