[IMP] website, *: introduce new classes to color snippets

*: web, web_editor, website_blog, website_event

New o_cc${xxx} classes where ${xxx} is a number [1-5] to style snippets:
they come with a background color, a text color, headings colors, a
link color, primary button colors and secondary button colors which
will later be possible to customize by the user.

The classes are made so that they are working on two levels. So if a
column receives a color class and the snippet too, everything will work
fine. More than 2 levels are not supported and the editor is made so
those cases should not appear. See o_colored_level class.

Part of https://github.com/odoo/odoo/pull/45856
task-2197038