[CI] Fixes to ivas-conformance job

• Related issues: None
• Requested reviewers: @kiene

Reason why this change is needed

• The ivas-conformance-linux fails on runners using pytest-html version < 4
• Cleanup of unused files in preparation of 26.252 package.

Description of the change

• scripts/parse_commands.py adapted to use also older version of pytest-html.
• scripts/cleanup_26252.py added to remove files that are not used in the 26.252 script.

Affected operating points

• None, CI only