[REF] web_editor, website: adapt wysiwyg to 12.0 editor

The wysiwyg abstraction layer was introduced in saas-12.2 by
commit f2969923. Its goal was to provide an external interface
for other modules that wanted to use the editor feature such
that the editor core itself could be changed without requiring
extensive changes in the other modules.

This commit is adapting the wysiwyg interface to instantiate
the 12.0 editor below it rather than the saas-12.2 one, thus
reverting the "new editor" part of f2969923 itself.

Part of PR 35677.

Co-authored-by: Nicolas Bayet <nby@odoo.com>
Co-authored-by: Antoine Guenet <age@odoo.com>
Co-authored-by: Christophe Matthieu <chm@odoo.com>
Co-authored-by: David Monjoie <dmo@odoo.com>