Roll back appendable CSV data

[danielballan]

We made CSV data sources appendable to have a quick proof of concept, used with a single-process server to prototype flyscanning. But appending file-based storage is not safe/robust in a horizontally scaled deployment. #779 provides a better way. It includes support for single-process (DuckDB) or scaled (PostgreSQL) storage. I think therefore we should remove support for appendable CSVs.

This is blocked by releasing #779 and then releasing a version of TiledWriter in bluesky that uses SQL instead of CSV.