[CI] Add files generated with prepare_combined_format_inputs.py and remove fixture to call the script

• Related issues: sa4/audio/ivas-basop!1800 (comment 77877)
• Requested reviewers: @kiene

Reason why this change is needed

• Pipelines are failing due to missing files for combined formats.

Description of the change

• Output of prepare_combined_format_inputs.py added to testv
• Removed fixture to call the script

Affected operating points

• All tests should be the same, but hopefully the occasional failure will disappear.