Implement Buffer Protocol for PandasBuffer
See https://github.com/pandas-dev/pandas/pull/55227#discussion_r1370815016
Need to investigate the validity buffer in more detail. Arrow would use bits for that so some of the sizing may be off, if that hasn't already been converted to bytes elsewhere in the interchange  This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. Closing for now - may revisit later