[MERGE] various: Make the test suite demo data independant

Purpose
=======

This is the first huge step to improve the test suite in several ways:

- Make them demo data independent, allowing to modify the demo data without having to adapt the tests depending on it. It also allows to have a beautiful + convenient demo dataset to make a demonstration, and to configure complex data in the tests to manage the corner cases.
- Improve the test performances by converting them into SavepointCase. Each test will be rollbacked to it's initial state, after the setUpClass call. That way the different data are not re-created at each test for nothing.
- Introduce several test classes in base/tests/common.py to launch a TransactionCase, HttpCase or SavepointCase test with an available demo user, portal user or a large set of partners.
- This is the first step to tend to a rolling release process, allowing to execute the tests (or a subset of the tests) on a migrated base, for example.

closes odoo/odoo#39868

Taskid: 2075739
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>

addons/website/static/src/js/tours/banner.js

@@ -15,6 +15,7 @@ tour.register("banner", {
     position: "bottom",
 }, {
     trigger: "#snippet_structure .oe_snippet:eq(1) .oe_snippet_thumbnail",
+    extra_trigger: "body.editor_enable.editor_has_snippets",
     content: _t("Drag the <i>Cover</i> block and drop it in your page."),
     position: "bottom",
     run: "drag_and_drop #wrap",