Add PathName as default to extract for CytoTable

In a recent PR, FileName columns were automatically added into presets to be extracted. Since CytoDataFrame can also use the PathNames instead of context directories given that datasets can be become a bit complex and nested, CytoTable should also extract these columns.

Review the recent PR that automatically added FileName columns to extraction presets, then compare that behavior with CytoDataFrame's use of PathNames. The work is complete when CytoTable presets extract PathName columns by default for nested datasets, with behavior consistent with the existing FileName handling.

Written by the indexing model from the issue text.