Expand icepyx to read s3 data

[rwegener2]

Goal

NSIDC has put IS-2 data in the cloud, so we would like icepyx to be able to access that data for users. ☁️💙

How it was done

The EarthdataAuth class was added as a mixin to the Read class. The product and version are read from the file the same way they are read in using a local file. The python standard glob module does not accept s3 paths, so s3 paths are not glob-able (i.e. the user must always give the full exact filepath). There is an s3 version of glob, so this could be implemented in the future. Mixed lists of s3 paths and local paths are not allowed. If a user tries to load more than two files or three data variables at the same time they are given a warning that discourages continuing and requires user confirmation to proceed.

Very loose timing suggests that it takes about 5 minutes per data variable per file to load s3 data (testing on the dem_h variable of an ATL09 file). Running two files took 11 minutes.

How to test it

from icepyx.core.read import Read

s3_path = 's3://nsidc-cumulus-prod-protected/ATLAS/ATL09/006/2020/06/18/ATL09_20200618112352_12820701_006_01.h5'
reader = Read(s3_path)
reader.vars.append(var_list=['dem_h'])
reader.load()

[rwegener2]

Alright this PR is ready for re-review. Changes since the last review:

• addressing this catch from @JessicaS11 about asking for authentication even for local reads
• fix a small error about parsing bytes for reading ATL03
• update the cloud tutorial notebook

[JessicaS11]

@rwegener2 I wanted to trigger the _confirm_proceed() so I passed in a list of s3 urls... I got the confirmation, but the warning never showed (and the confirmation is confusing without it). Wondering if it makes sense to kick the warning into the function?

[rwegener2]

Hm, interesting. The warning appeared when I was running it. That was a few commits back, though, so 🤷‍♀️
I think it's fine to add the warning to the _confirm_proceed() function. My guess is that either way we'll need to increase the stacklevel to 3 or 4 if the warning isn't showing up at level 2.

[JessicaS11]

I seem to recall I was messing with the warnings settings in my hub for a presentation recently... since this is an important one, I added a cell to turn warnings on (changing the stack level didn't help in my case). Let me know if you think we should take a different approach. (EDIT: I left the warning where it was since the message depends on what triggers the confirmation.) Otherwise, this should be good to go.