Add runtime support for AWS Security Token Service

[lesserwhirls]

See #194 (specifically #194 (comment)).

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This change is 

[WeatherGod]

Running an experiment now on my system by copying the sts-2.17.156.jar over into webapps/thredds/WEB-INF/lib/ in the unidata/thredds-docker:5.4 image, since my CI/CD is currently set up to use that.

[WeatherGod]

Success!

While I didn't specifically test out this patch, I can confirm that just simply adding the sts jar file to the classpath will allow thredds to host S3 data when running in EKS (and possibly ECS?).

[WeatherGod]

Would it also be worth adding at least some notes on how to add logging for the aws sdk to the documentation? Personally, I would leave out the http part as that made the logs unbearably noisy. The awssdk specific parts were absolutely crucial in figuring this problem out, and I would imagine it would be helpful going forward for any other user trying to debug S3 issues.

[tdrwenski]

@WeatherGod I will have a look at adding aws sdk logging in a separate PR-- probably just warn and higher to prevent noise.

[WeatherGod]

Fair enough. I'll note that I initially tried setting them to info, and got no output. So, even the failure to load the sts module when the appropriate environment variable was found was buried as a "debug". But even just having the entries in the logging eonfigs will give users a foothold to turn the logs on when they need it.

[tdrwenski]

@WeatherGod you can see my PR here: #298. I also added something to the FAQs, so hopefully that could be helpful. Feel free to comment there if you have suggestions!