Allow filtering of projected fields

[westonpace]

Users can introduce new fields using projection. However, they cannot turn around and filter on these fields. This can perhaps wait until we have general SQL support but it could be implemented earlier.

The challenge is that we compile filters against the scan input schema and this does not contain the projected fields. We should compile the filter against the final projected schema. Then we can subtract fields that don't exist in the scan input schema and add a final FilterExec after the project.

This is a little bit tricky because, if we do the above directly, then the take step will try and take these fields and not find them. So we need to change the take logic slightly as well.

[westonpace]

I'm labeling this "good first issue" because all the changes will be mostly in the scanner module (e.g. don't need whole system knowledge). However, the scanner module is fairly complex and so I don't mean to imply that this would be an easy first issue :)