Add fallback support for viewing arrow files locally.

[bloodearnest]

We want to encourage users to use arrow files for ehrql outputs.

The main drawback of this is viewing these files in local development. We hope that users using codespaces/vscode can use an arrow dataset viewer plugin (opensafely/research-template#56)

However, it may be that users are not using vscode, and need a way to easily view arrow files generated by local ehrql runs.

Previously, when addressing this problem for csv.gz files, we added a unzip command to extract a copy to a regular CSV for local viewing: #110

We could possibly do the same here, and add an opensafely csv path/to/file.arrow or similar that would load and write a path/to/file.csv file for easy local viewing as a simple fall back for this.