[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/finance/accounting/bank/feeds/ponto.rst

@@ -6,7 +6,7 @@ Ponto as bank synchronization provider
 place and directly see all their transactions within one app. It is a third-party solution that is
 continuously expanding the number of bank institutions that can be synchronized with Odoo.
 
-.. image:: media/ponto-logo.png
+.. image:: ponto/ponto-logo.png
    :align: center
    :alt: Logo of the Ponto brand
 
@@ -30,7 +30,7 @@ Link your bank accounts with Ponto
 #. Create an account if you don't have one yet.
 #. Once you are logged in, create an *organization*.
 
-   .. image:: media/ponto-organization.png
+   .. image:: ponto/ponto-organization.png
       :align: center
       :alt: Fill out the form to add an organization in Ponto.
 
@@ -39,7 +39,7 @@ Link your bank accounts with Ponto
 #. Select your country, your bank institutions, give your consent to Ponto, and follow the steps
    on-screen to link your bank account with your Ponto account.
 
-   .. image:: media/ponto-add-account.png
+   .. image:: ponto/ponto-add-account.png
       :align: center
       :alt: Add bank accounts to your Ponto account.
 
@@ -57,7 +57,7 @@ Link your Ponto account with your Odoo database
    **all the accounts** you want to synchronize. Even the ones coming from other banking
    institutions.
 
-   .. image:: media/ponto-select-accounts.png
+   .. image:: ponto/ponto-select-accounts.png
       :align: center
       :alt: Selection of the accounts you wish to synchronize with Odoo.