Test secrets

DuckDB only allows persistent secrets with the x00 permission (e.g. 600 or 700). Therefore to use these secrets, the permissions need to be set before running any tests that uses them.

The recommended way to add tests that touch these persistent secret files is to put them behind a

require-env TEST_PERSISTENT_SECRETS_AVAILABLE

statement, which ensures the tests only run in CI jobs where the permissions are set correctly.