[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/getting_started/initial_configuration/chart_of_accounts.rst

@@ -22,7 +22,7 @@ time, they are listed as follows :
 When browsing your Chart of Accounts, you can filter the accounts by number, in the left column, and
 also group them by Account Type.
 
-.. image:: media/chart_of_accounts01.png
+.. image:: chart_of_accounts/chart_of_accounts01.png
    :align: center
    :alt: Group the accounts by type in Odoo Accounting
 
@@ -145,7 +145,7 @@ To display your **Trial Balance** report with your Account Groups, go to :menuse
 --> Reporting --> Trial Balance`, then open the *Options* menu and select **Hierarchy and
 Subtotals**.
 
-.. image:: media/chart_of_accounts02.png
+.. image:: chart_of_accounts/chart_of_accounts02.png
    :align: center
    :alt: Account Groups in the Trial Balance in Odoo Accounting
 

content/applications/finance/accounting/getting_started/initial_configuration/setup.rst

@@ -21,7 +21,7 @@ Accounting onboarding banner
 
 The step-by-step Accounting onboarding banner is composed of four steps:
 
-.. image:: media/setup_accounting_onboarding.png
+.. image:: setup/setup_accounting_onboarding.png
    :align: center
    :alt: Step-by-step onboarding banner in Odoo Accounting
 
@@ -39,7 +39,7 @@ This menu allows you to add your company’s details such as the name, address,
 number, email address, and Tax ID, or VAT number. These details are then displayed on your documents,
 such as on invoices.
 
-.. image:: media/setup_company.png
+.. image:: setup/setup_company.png
    :align: center
    :alt: Add your company's details in Odoo Accounting and Odoo Invoicing
 
@@ -105,7 +105,7 @@ opening balances.
 Basic settings are displayed on this page to help you review your Chart of Accounts. To access all
 the settings of an account, click on the *double arrow button* at the end of the line.
 
-.. image:: media/setup_chart_of_accounts.png
+.. image:: setup/setup_chart_of_accounts.png
    :align: center
    :alt: Setup of the Chart of Accounts and their opening balances in Odoo Accounting
 
@@ -125,7 +125,7 @@ If you have Odoo Accounting installed on your database, you can reach it by goin
 
 The Invoicing onboarding banner is composed of four main steps:
 
-.. image:: media/setup_invoicing_onboarding.png
+.. image:: setup/setup_invoicing_onboarding.png
    :align: center
    :alt: Step-by-step onboarding banner in Odoo Invoicing
 
@@ -155,7 +155,7 @@ automatically adds the company's phone number, email, website URL, and Tax ID (o
 footer, according to the values you previously configured in the :ref:`Company Data
 <accounting-setup-company>`.
 
-.. image:: media/setup_document_layout.png
+.. image:: setup/setup_document_layout.png
    :align: center
    :alt: Document layout configuration in Odoo Invoicing