[C++] Move csv::ReadOptions::skip_rows to csv::ParseOptions::skip_rows

[asfimport]

This properly affects how the CSV is parsed and in turn the schema and data, so it belongs in ParseOptions. This means it can also be configured in Datasets.

For now, we'll duplicate the field and deprecate the original spot.

Reporter: David Li / @lidavidm
Assignee: David Li / @lidavidm

Related issues:

• [C++][Dataset] Add ConvertOptions and ReadOptions to CsvFileFormat (relates to)

_{Note: This issue was originally created as ARROW-12002. Please see the migration documentation for further details.}

[asfimport]

David Li / @lidavidm:
On further reflection this would be a good deal of churn for not much of an improvement, so cancelling this.