[IMP] getting_started: use odoo/tutorials repository + runbot

We now use the odoo/tutorials to make the technical onboarding.
- Change the current documentation accordingly.
- Add a section for employees only so that they use odoo-dev/tutorials
as shared fork. It's closer to our way to work so we think it's better
to make them use to it as fast as possible.
- Add some explanations about runbot.

`odoo/technical-training-sandbox` will no longer be used and can be considered deprecated.

closes odoo/documentation#7968

Signed-off-by: Claire Bretton (clbr) <clbr@odoo.com>

content/developer/tutorials/getting_started/03_newapp.rst

@@ -56,7 +56,7 @@ Prepare the addon directory
       :align: center
       :alt: The new module appears in the list
 
-The first step of module creation is to create its directory. In the `technical-training-sandbox`
+The first step of module creation is to create its directory. In the `tutorials`
 directory, add a new directory :file:`estate`.
 
 A module must contain at least 2 files: the ``__manifest__.py`` file and a ``__init__.py`` file.
@@ -77,8 +77,8 @@ be uninstalled**. Think about your favorite Linux distribution package manager
 
     Create the following folders and files:
 
-    - ``/home/$USER/src/technical-training-sandbox/estate/__init__.py``
-    - ``/home/$USER/src/technical-training-sandbox/estate/__manifest__.py``
+    - ``/home/$USER/src/tutorials/estate/__init__.py``
+    - ``/home/$USER/src/tutorials/estate/__manifest__.py``
 
     The ``__manifest__.py`` file should only define the name and the dependencies of our modules.
     The only necessary framework module for now is ``base``.