[REM] *: remove new content controllers

*: website_event, website_event_sale, website_forum, website_sale,
   website_sale_slides, website_slides, website_slides_forum

This commit removes the remaining controllers that are no longer used
since the use of form views on website new content dialogs (following
the website in backend merge at [1] and the many iterations afterwards).

With the website in backend work, a feature was lost for the creation of
events: dummy tickets were created. This commit actually removes the
feature for good. Events default values are managed by templates.
Moreover there are links in frontend to edit the event when being
allowed to edit it (event groups), notably when there is no ticket in
registration page. So it makes no sense to create dummy tickets, without
price, for 1000 seats. Those values are random so they will have to be
edited. Better let users create real tickets if necessary, than editing
and/or removing dummy tickets.

[1]: https://github.com/odoo/odoo/commit/31cc10b91dc7762e23b4bde9b945be0c4ce3fe3b



task-2687506

closes odoo/odoo#99042

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