middleware: add LoggerConfig with Skipper func

[kraem]

breaking change.

can handle both

CreateLoggerMiddleware(LoggerConfig{}, ...)

and

CreateLoggerMiddleware(DefaultLoggerConfig,, ...)

[larsve]

Not sure how many depends on EAL, but I would prefer to add this as a non-breaking change, i.e. add a new public method that take the new confg param and change CreateLoggerMidleware to return the result of the new method with an empty config.

[larsve]

Maybe we should think of adding a second type of skipper, that just skip logging (unless there is an error). We use that to "mute" all logging of k8s health checks that otherwise would get logged.