[MOV] content/*: move resource files into their related page's directory

Since odoo/documentation#903, the guideline for the location of new
resource (images, downloadable files, RST includes...) files is to place
those inside the directory of the RST page that references them.

For example, if `doc1.rst` has a reference to `image.png` and to
`download.zip`, the file structure should look like this:

├── parent_doc/
│     └── doc1/
│     │     └── image.png
│     │     └── download.zip
│     └── doc1.rst
│     └── doc2.rst
├── parent_doc.rst

Before this commit, most of the resource files were still located inside
'media' directories holding all the resource files referenced by RST
pages located at the same level as these directories. In the example
above, a single 'media' directory would hold all the resource files
referenced by both `doc1.rst` and `doc2.rst`. Doing so prevented us from
figuring out easily which resource file was referenced by which RST page
and, thus, lead to unused resource files piling up in the repository. It
also made it more complicated to define codeowners regex rules because a
team could not simply be assigned to `/some_page.*` but needed to be
assigned to both `/some_page\.rst` and to the location of 'media'.

In order to help new content writers figure out the guideline when
taking examples from other RST pages, this commit retroactively applies
the guideline to existing resource files and 'media' directories. The
left-over resource files that are not referenced by any RST page are
removed.

task-2497965

Part-of: odoo/documentation#2068

content/applications/general/auth/2fa.rst

@@ -46,31 +46,31 @@ Once you have your authenticator of choice, go to the Odoo instance
 you want to setup :abbr:`2FA (two-factor authentication)`, then open
 :guilabel:`Preferences` (or :guilabel:`My Profile`):
 
-.. figure:: media/totp_setup/preferences.png
+.. figure:: 2fa/preferences.png
     :align: center
 
 Open the :guilabel:`Account Security` tab, then click the
 :guilabel:`Enable two-factor authentication` button:
 
-.. figure:: media/totp_setup/sec_tab.png
+.. figure:: 2fa/sec_tab.png
    :align: center
 
 Because this is a security-sensitive action, you will need to input
 your password:
 
-.. figure:: media/totp_setup/sec_enhanced.png
+.. figure:: 2fa/sec_enhanced.png
    :align: center
 
 After which you will see this screen with a barcode:
 
-.. figure:: media/totp_setup/totp_scan.png
+.. figure:: 2fa/totp_scan.png
    :align: center
 
 In most applications, you can simply *scan the barcode* via the
 authenticator of your choice, the authenticator will then take care of
 all the setup:
 
-.. figure:: media/totp_setup/scan_barcode.jpg
+.. figure:: 2fa/scan_barcode.jpg
    :align: center
 
 .. note::
@@ -80,17 +80,17 @@ all the setup:
    click the provided link, or copy the secret to manually set-up your
    authenticator:
 
-   .. figure:: media/totp_setup/secret_visible.png
+   .. figure:: 2fa/secret_visible.png
       :align: center
 
-   .. figure:: media/totp_setup/input_secret.png
+   .. figure:: 2fa/input_secret.png
       :align: center
 
 Once this is done, the authenticator should display a *verification
 code* with some useful identifying information (e.g. the domain and
 login for which the code is):
 
-.. figure:: media/totp_setup/authenticator.png
+.. figure:: 2fa/authenticator.png
    :align: center
 
 You can now input the code into the :guilabel:`Verification Code`
@@ -100,7 +100,7 @@ button.
 Congratulation, your account is now protected by two-factor
 authentication!
 
-.. figure:: media/totp_setup/totp_enabled.png
+.. figure:: 2fa/totp_enabled.png
    :align: center
 
 Logging in
@@ -112,7 +112,7 @@ On the login page, input the username and password of the account for
 which you set up :abbr:`2FA (two-factor authentication)`, rather than
 immediately enter Odoo you will now get a second log-in screen:
 
-.. figure:: media/totp_setup/2fa_input.png
+.. figure:: 2fa/2fa_input.png
    :align: center
 
 Get your authenticator, input the code it provides for the domain and