[IMP] website_slides: add an overview (kanban view) on course model

PURPOSE

eLearning should have its own application in manager. Indeed this is becoming
a big application and having it embedded inside Website application is not
enough anymore. It should also hold updated and easy-to-use menus,
navigation, actions and views in backend.

SPECIFICATIONS

Add course (slide.channel) kanban view. Each tile should contain

  * Title of the course (make it big, o_primary)
  * Tags below the title
  * Primary button "New Lesson"
  * Statistics :
    * Attendees
    * Running (progress != 100%)
    * (if one content is certificate) Certified or Finished
  * See
    * v1: https://drive.google.com/a/odoo.com/file/d/13K8FmkbwmBG4JQ5gH3Q5T8OlWPs3blcu/view?usp=drivesdk

With FP remarks https://drive.google.com/a/odoo.com/file/d/1mb7LUT0VUNs5fMcKB9c0Bfaqk2-XFFuu/view?usp=drivesdk


  * remove globe, type and visibility of course, lessen padding between rating
    views and watch time;
  * for rating, instead of 8.00 => 5 reviews (4.5/5);
  * replace "View Lesson" / "Invite" by "View Course" => Send to the front-end
  * In the menu of the card, add:
    * Invite (same behavior than before, when it was a primary btn)
  * click on x Contents:  land on the contents, group by category with sequence
  * re-order of the 3 infos/Stats at the bottom of the card: 1. Content,
    2. Attendee, 3. Certified
    * + number: font-weight: 500 + font-size 1.2em
    * + labels: remove text-uppercase, + text-color: #666666
    * + the "whole box" is clickable

LINKS

Task 1978729
PR #35061

Co-Authored-By: Thibault Delavallée <tde@odoo.com>
Co-Authored-By: Jérémy Hennecart <jeh@odoo.com>