[CLI] Drop legacy printing helpers from `_cli_utils.py` (#4285)
* [CLI] Drop legacy printing helpers from `_cli_utils.py`
Now that every command has migrated to the `out` singleton, the legacy
helpers in `_cli_utils.py` have no callers. The one exception was
`api_object_to_dict`, which still served dataclass→dict conversion before
`out.table` / JSON serialization — and `_output.py` already exposes the
same helper as `_dataclass_to_dict`. So:
- Switch every caller (discussions, models, datasets, papers, spaces,
collections, _file_listing) from `api_object_to_dict` to
`_dataclass_to_dict` from `_output.py`.
- Delete from `_cli_utils.py`: `api_object_to_dict`, `_serialize_value`,
`print_as_table`, `print_list_output`, `_format_cell`, `_format_value`,
`_to_header`, `_MAX_CELL_LENGTH`, plus the legacy option types and
enum (`OutputFormat`, `_set_output_mode`, `FormatOpt`, `FormatWithAutoOpt`,
`QuietOpt`). Remove now-orphaned imports (`json`, `dataclasses`,
`datetime`, `tabulate`, `Union`).
- Update `tests/test_cli_output.py` to import `OutputFormatWithAuto`
from `_output.py` directly instead of via the `_cli_utils.py` re-export.
No behavior change.
* [CLI] Rename `OutputFormatWithAuto` to `OutputFormat` (#4286)
The legacy `OutputFormat` (table | json) was removed in the previous
cleanup PR, freeing up the name. `OutputFormatWithAuto` was always the
"real" enum — covering auto/human/agent/json/quiet — so drop the
disambiguating suffix.
Pure rename, no behavior change. Also removes the now-stale TODO
comment in `_output.py` that referenced the (now deleted) legacy enum.