make edx-platform log configurable

[pdpinch]

As a devops/sre, I'd like to be able to configure the logging format, structure and potentially add new log handlers by passing configuration to the log function at https://github.com/edx/edx-platform/blob/master/openedx/core/lib/logsettings.py#L13

It would be beneficial to expose more customizability to how the logging is set up. For instance, either make this function more flexible, so that it can accept a dict_config that gets merged with the one inside the function, or moving the log configuration into the settings module so that it can be managed in the same way as the other configuration values.

acceptance criteria

• write an ADR describing the approach and open a PR upstream in edx-platform for it
• when there is consensus about the approach merge the ADR and open another PR with the implementation.

[pdpinch]

Is this still needed?