Add preprocess by shank

[JoeZiminski]

This PR adds the ability to preprocess a recording by group. This entails splitting the recording, applying preprocessing, and then aggregating at the end.

Initially, for each step the recording was split, preprocessed, then aggregated. However, this led to very slow behaviour when using the get_traces() function, it does not appear aggregate_channels is best used in this way. Instead, the recording is split at the start. For each preporcessing step, the preproecssing is applied, and a aggregated version of the recording is stored on preprocess_data for provenance. However, the split recording are kept and each preprocessing step is applied to these separately. Then at the end, this split recording is finally reaggregated. This means that for each stored preprocessing step the data is aggregated and it is aggregated in the final step, but for each step the aggregation only happens once.