This update reorganizes automated test and guided tour files into a clearer structure and connects them to a dedicated test asset bundle. It also makes debug settings persist through the user session, reducing repeated setup and improving reliability for development and testing workflows.

Counterpart of https://github.com/odoo/odoo/pull/33213

Document thumbnails are now generated using a more reliable image processing flow that better handles different image types. If thumbnail creation fails, the system now safely records that no thumbnail is available instead of risking incorrect results.

rebase-ff