Runtime AWS region selection

[mrballcb]

I have clusters I want to test this on, but none of them are in eu-west-1. I forked the repo and added this feature (with some hackey and really ugly golang) that gets the AWS_REGION from an environment variable. Please feel free to critique and provide suggestions as to how it can be better. I didn't create a PR, I wanted to see how it was received first.

Branch: https://github.com/mrballcb/kubernetes-cost-report/tree/aws-region-env-var
Commit: main...mrballcb:kubernetes-cost-report:aws-region-env-var

I built a docker image of the above and put it at:
https://hub.docker.com/repository/docker/mrball/cost-report

I am currently testing it on one of my clusters.