Add option to also log to a file

There are setups with kuberenetes that require logs to be written to a file, so that they can then be uploaded to the log aggregators. Just logging to stdout does not allow for this.

We do want to always log to stdout, since that's how all debugging is done in Kubernetes, but we should have an option to **also** log to a file.

Start by locating the operator's logging setup and the configuration or command-line entry point where logging options are defined. Confirm how logs are currently sent to stdout, then define how an opt-in file destination should work while preserving stdout; done means both destinations receive logs when the option is enabled.

Written by the indexing model from the issue text.