Setting metadata for interval in input tests does not work

[lldelisle]

Describe the bug
If you write a test in a workflow or a tool and you want to use the metadata for interval. For example:

      <param name="input" value="droPer1.gff" ftype="interval" >
        <metadata name="chromCol" value="1"/>
        <metadata name="startCol" value="4"/>
        <metadata name="endCol" value="5"/>
      </param>

The metadata is not used and the startCol is still 2 (the default) and endCol is still 3 (the default)

Galaxy Version and/or server at which you observed the bug
Galaxy Version: any up to date

To Reproduce
Steps to reproduce the behavior:
I wrote a PR with a test included into the Framework tests which simply print the 3 metadata columns: #14869
And the test fails with:

FAILED test/functional/test_toolbox_pytest.py::TestFrameworkTools::test_tool[metadata_interval/1.0.0-0] - galaxy.tool_util.verify.interactor.JobOutputsError: Output output_of_input_metadata:  different than expected
Expected line '1 4 5' in output ('1 2 3
')