Clean up temporary files when running tests

[asfimport]

The test suite writes a ton of files (upwards of 10GB) to disk, but does not clean them all up. This unnecessarily clutters storage.

Reporter: Atour Mousavi Gourabi / @amousavigourabi

PRs and other links:

• GitHub Pull Request #1261

_{Note: This issue was originally created as PARQUET-2421. Please see the migration documentation for further details.}