Add data-aware saving pattern to the s3 adapter

s3read("default/xgb")
s3read("default/xgb_data_label")

now training data does not live in the tundraContainer anymore
hopefully besides model and training data necessary to redo the diagnoistics of model, we won't see the situation of exponential growing s3.* in the future. if so, then we parametrize s3....