(SE) Cleaning up Logger implementation

[mranst]

In adding type hinting for swell, we discovered that the implementation of Logger could be improved:

• Implement Logger (from swell.utilities.logger) as an inherited class of logging.Logger. This would simplify annotations and make it possible for swell code to simply use logging.Logger where sufficient

This would resolve possible confusion in cases such as in slurm_test.py, which passes a logging.Logger object to SWELLError, where most other functions specifically expect a swell logger.