Better way to store test and notebook data

[ctuguinay]

Currently, most test files are stored on the current commit for the main branch, with the contains_transect_zip branch containing a larger .zip file containing a calibrated Sv data product from Echopype. This separation was made since PyPi has a 100MB limit to what they are allowing to host.

I think I'll wait until GSOC and other contributors address Echopype's OSOceanAcoustics/echopype#1263 and just emulate what was done there.