fix(mfdataplist): fix multiple issues (#2775)

Fix some cases where MFPandasList behaved inconsistently with MFList/MFTransientList

- support None period data, fixed in set_record (added record["data"] is not None)
- convert 0- to 1-based indexing for non-cell-ID fields marked with numeric_index
- support external file paths via open/close, fixed with new branch in set_data()

These were flushed out by MODFLOW-ORG/modflow6#2868, which added # package-type stress-package to a number of DFNs. Since the pandas alternative list impl was added in #1955, list blocks in stress packages use MFPandasList by default while other packages use the old MFList, due evidently to some gaps in the pandas approach.

Also some related refactoring/fixes/cleanup

- support DIS2D/DISV1D/DISV2D cell IDs
- add _get_cellid_columns() helper to centralize cellid column logic
- delete _unique_column_name(), _untuple_manually()
- fix a typo in mffileaccess.py (cellid_nodes → cellid_node)

Author: wpbonelli