[python] Handle non-list/non-tuple input in tiledbsoma.io registration

[johnkerl]

Doing this

    tiledbsoma.io.register_h5ads(
        experiment_uri=exp_uri,
        h5ad_file_names=h5ad_file_name,
        measurement_name="measname",
        obs_field_name=obs_field_name,
        var_field_name=var_field_name,
    )

instead of

    tiledbsoma.io.register_h5ads(
        experiment_uri=exp_uri,
        h5ad_file_names=[h5ad_file_name],
        measurement_name="measname",
        obs_field_name=obs_field_name,
        var_field_name=var_field_name,
    )

results in a cryptic error.

[sc-61390]