[FIX] base: do not search for attachment for related fields in _binary_record_content

Use case: website_event_track(_online)
======================================

On sponsor model, image_128 field is defined in website_event_track module as
computed stored Image field. It means that when this binary field is set, an
attachment is created in ir.attachment model -> attachment is set to True.

In website_event_track_online module this field is modified. It is set as
a related (resized) version of image_512 and not stored anymore.

However attachments still exist in ir.attachment table for sponsor records.
This is not an issue when trying to access the image_128 field using the ORM
as the compute (or related) is correctly called. However '/web/image' does
checks if the field has an attachment and loads it. In our case old attachments
still in database are therefore displayed instead of the new related image.

Fix
===

When checking for an existing attachment in _binary_record_content we also
check that the field is not a related. This fixes the current issue. It also
makes _binary_record_content work as the ORM, aka using the computed value
and not any stored information.

DB Cleaning
===========

In 14.0 a script will be added to clean existing attachments for sponsor
model. Indeed there is no need to keep unused attachments. Especially in
14 website_event_track_online has been merged in website_event_track, meaning
only existing db have to be cleaned. New DBs will never have this attachment
issue as the field is always computed.

Task ID: 2341108

closes odoo/odoo#60259

X-original-commit: ada1eab338c6cffb526b03377ec01962f9c26c4c
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

odoo/addons/base/models/ir_http.py

@@ -377,7 +377,7 @@ class IrHttp(models.AbstractModel):
         filehash = 'checksum' in record and record['checksum'] or False
 
         field_def = record._fields[field]
-        if field_def.type == 'binary' and field_def.attachment:
+        if field_def.type == 'binary' and field_def.attachment and not field_def.related:
             if model != 'ir.attachment':
                 field_attachment = self.env['ir.attachment'].sudo().search_read(domain=[('res_model', '=', model), ('res_id', '=', record.id), ('res_field', '=', field)], fields=['datas', 'mimetype', 'checksum'], limit=1)
                 if field_attachment: