[FIX] doc: correct erroneous installation instructions

This commit corrects erroneous instructions in the documentation page for the installation of Odoo.

Additionally, the following changes are made:
- Add new instructions where the steps were not clear or complete enough.
- Replace some installation flows for an easier onboarding.
- Rework some parts of the page structure and display.
- Add a "running odoo" section for Mac OS.
- Fix display error in views.rst

task-2072822

closes odoo/odoo#40319

Signed-off-by: Christophe Monniez (moc) <moc@odoo.com>

doc/reference/views.rst

@@ -1088,17 +1088,17 @@ take the following attributes:
 
   Example: tasks have a field user_id that reference res.users. The res.users model has a field image that holds the avatar,
   then:
-.. code-block:: xml
 
-      <gantt
+  .. code-block:: xml
+
+     <gantt
         date_start="date_start"
         date_stop="date_stop"
         thumbnails="{'user_id': 'image_128'}"
       >
       </gantt>
 
-
-will display the users avatars next to their names when grouped by user_id
+  will display the users avatars next to their names when grouped by user_id.
 
 .. _reference/views/diagram: