GSConfig should not affect log level setting

GSConfig is a wrapper object for GraphStorm but it includes code that enforces log level at the application level:

https://github.com/awslabs/graphstorm/blob/f0c38bbc2809dbbe2a956a93a31ba216fff13473/python/graphstorm/config/argument.py#L190-L198

The caller program should get to establish the logging level, using `logging.basicConfig(level=log_level, force=True)` overrides user intent, especially when the GraphStorm API is used.

Start with python/graphstorm/config/argument.py at lines 190-198 and inspect how GSConfig configures logging. Verify that callers can establish their own level without GraphStorm overriding it; done means the wrapper no longer forces the application-wide log level.

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