Added biahub convert

[srivarra]

No description provided.

[ieivanov]

This is much more code duplication than I expected. If needed, let's refactor concatenate such that we can reuse it here. In my mind, biahub convert should be more or less something like

from biahub.concatenate import concatenate

@click.command("convert")
...
def convert_cli(
    input_position_dirpaths: List[Path],
    output_dirpath: Path,
...
) -> None:

  concatenate(input_position_dirpaths, output_dirpath)