csv: use universal newlines

This fixes reading CSVs with unusual newlines, like \r. We should use
this in all places that we read CSVs, in case they were produced by
systems that use those newlines.

FileMaker, for example, still outputs CSV with \r to this day, even
though MacOS transitioned to \n in 2001.

Fixes #7015.
Remove popup metadata reminder

This is no longer needed now that there are ways to ensure that there's
an opportunity to input metadata before it's finalized.

Fixes #7013.