Handle AWS Cloudformation Throttling More Gracefully

[dissolved]

We see frequently errors due to AWS throttling. Increasing the number of retries (the default was set to 3 retries) resolves the problem. The sdk does an exponential backoff, and 3 retries was not sufficient for our needs.

Considerations

This PR only increases the number of retries for cloudformation, but potentially, many of the AWS services may benefit from an increase in the retry limit. Additionally, I didn't see an established way for user configuration of such a constant (though imagine this could be set via the Staxfile. I chose to make it configurable via ENV var, but I can change that if there is a more preferred way. Lastly, I arbitrarily made the retry limit very high (100). The thought here was ctrl-c is your friend, but I honestly have no idea what a reasonable retry limit should be.

[rlister]

This is great, thanks! Let's try it with 100, which may well be too high, but we'll drop it if necessary. We can also try a retry_backoff proc to bump up the amount of exponential backoff if necessary to avoid throttling.

[dissolved]

@rlister The docs also references a retry_jitter which apparently setting to :full might improve things, but for some reason it didn't recognize the parameter. I didn't dig deeper. Article on jitter here: https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/