Allow uploading pre-computed feature .nc files to s3 buckets using similar functionality as for DataAssemblies/StimulusSets

Currently, DataAssemblies and StimulusSets are possible to upload to appropriate s3 buckets using [brainio.packaging](https://github.com/brain-score/brainio/blob/main/brainio/packaging.py), but `.nc` files with pre-computed features are not.

It would be substantially more convenient to allow similar functionality for `.nc` files with pre-computed features, especially when submitting lots of benchmarks.