Always use EDL user token to fetch s3 creds

[chuckwondo]

This doesn't change any functionality, but speeds up fetching of s3 credentials by about 4x based on very primitive benchmarking, due to always using an EDL (bearer) token for fetching temp creds, rather than using EDL username/password (basic auth):

from timeit import timeit
import earthaccess

auth = earthaccess.login()

# These 2 lines are necessary only when running against
# earthaccess code that does not include the code in this PR,
# due to issue 1181, which this PR also fixes.
setattr(auth, "username", None)
setattr(auth, "password", None)

endpoint = "https://data.nsidc.earthdatacloud.nasa.gov/s3credentials"

print(timeit(lambda: auth.get_s3_credentials(endpoint=endpoint), number=10))

Benchmark results running on my pre-M1 MacBook:

• Without this PR: 36.76829030702356 (avg. of ~3.7s per s3 creds fetch)
• With this PR: 8.482286745973397 (avg. of ~0.85s per s3 creds fetch)
• Speedup: 36.76829030702356 / 8.482286745973397 ~= 4.33

The speedup is due to a reduction in the number of requests. In particular, using basic auth ends up making 4 times the number of requests than using a bearer token does, so the 4x speedup jives with reducing the number of requests by a factor of 4.

Fixes #1182
Fixes #1181

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---

📚 Documentation preview 📚: https://earthaccess--1183.org.readthedocs.build/en/1183/

[github-actions]

👈 Launch a binder notebook on this branch for commit abda5ca

I will automatically update this comment whenever this PR is modified

👈 Launch a binder notebook on this branch for commit 14fa683

[chuckwondo]

This is the crux of the fix for #1181, which also helps with the rest of the changes for #1182.

[chuckwondo]

Ruff ended up reformatting, which then put the noqa comment on the wrong line, which then made ruff complain about the print call, so this is just to satisfy ruff.

[betolink]

Just a couple questions in the code, this looks good and once get merge it we should release! @chuckwondo

[betolink]

Looks good @chuckwondo, I'm approving and waiting for another maintainer until tomorrow, if nobody has any objection I'll merge it in the morning.

[jhkennedy]

This looks good to me as well