Fix auto label and metric plotting

There seems to be some logistic errors in how Metric and Axis labels are set, such that when one plots a labelled axis like "offset", the labels are not correct. This seems to be related to some mechanism that propegates the dataset label name to the metric labels, but seems to also overwrite axis labels.

m = store.retrieve_data("dl3/instrument_response_functions/EffectiveArea.asdf")
m.plot()
plt.loglog()
plt.legend()

Expected behavior would be that the legend would have the offset bin names here.