[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/receivables/customer_payments/batch_sdd.rst

@@ -23,7 +23,7 @@ Go to :menuselection:`Accounting --> Configuration --> Settings`, activate **SEP
 (SDD)** and click on *Save*. Enter your company's **Creditor Identifier**. This number is provided
 by your bank institution, or the authority responsible for delivering them.
 
-.. image:: media/batch-sdd-creditor-identifier.png
+.. image:: batch_sdd/batch-sdd-creditor-identifier.png
    :align: center
    :alt: Add a SEPA Creditor Identifier to Odoo Accounting
 
@@ -39,7 +39,7 @@ money directly from their bank accounts.
 To create a new mandate, go to :menuselection:`Accounting --> Customers --> Direct Debit Mandates`,
 click on *Create*, and fill out the form.
 
-.. image:: media/batch-sdd-mandate-form.png
+.. image:: batch_sdd/batch-sdd-mandate-form.png
    :align: center
    :alt: Fill out SEPA Direct Debit in Odoo Accounting
 
@@ -78,7 +78,7 @@ Close or revoke a mandate
 Direct Debit mandates are closed automatically after their *End Date*. If this field is left blank,
 the mandate keeps being *Active* until it is *Closed* or *Revoked*.
 
-.. image:: media/batch-sdd-revoke-close.png
+.. image:: batch_sdd/batch-sdd-revoke-close.png
    :align: center
    :alt: Close or Revoke an SDD Mandate in Odoo Accounting
 
@@ -117,21 +117,21 @@ process all payments at once.
 To generate your XML file for the pending SDD payments, go to the related *bank journal* on your
 *Accounting dashboard*, then click on *Direct Debit Payments to Collect*.
 
-.. image:: media/batch-sdd-collect.png
+.. image:: batch_sdd/batch-sdd-collect.png
    :align: center
    :alt: Start the SDD payments collection in Odoo Accounting
 
 Select all the payments you want to include in your SDD XML file, then click on *Action* and select
 *Create Batch Payment*.
 
-.. image:: media/batch-sdd-batch.png
+.. image:: batch_sdd/batch-sdd-batch.png
    :align: center
    :alt: Create a batch payment with all the SDD payments in Odoo Accounting
 
 Odoo then takes you to your *Batch Payment*’s form. Click on *Validate* and download the SDD XML
 file.
 
-.. image:: media/batch-sdd-xml.png
+.. image:: batch_sdd/batch-sdd-xml.png
    :align: center
    :alt: Generate an XML file for your SDD payments in Odoo Accounting