Have upload_multichannel_drf_capture automatically scan channels

[rherban]

As an alternative to specifying a list of channels, have upload_multichannel_drf_capture upload all channels contained within when channels isn't specified.

[lucaspar]

Linking this doc page as a workaround for anyone interested:

https://sds.crc.nd.edu/sdk/common-workflows/capture-uploads/

The script auto-discovers channels from subdirectories containing drf_properties.h5 and it'd be similar to what an SDK implementation would do.