Remove psiresp.testing

[lilyminium]

psiresp.testing is a bad hack for patching QCFractal behaviour, making psiresp not quite independent.

Once the following issues are resolved, I need to check why I had to replace the storage in FractalSnowflake

I had to replace this because FractalSnowflake calls TemporaryPostgres calls PostgresHarness. So we are all clear to remove once issues are gone.

Steps to remove psiresp.testing:

• delete the file
• update the tests
• update the examples and documentation (!!)
• update environment pins

Issues:

• Cannot pass existing temporary directory to TemporaryPostgres MolSSI/QCFractal#698
• Cannot restore database MolSSI/QCFractal#697
• Cannot connect to database via Unix socket MolSSI/QCFractal#696