New Test Pattern for Unit Testing in Cloud-Nuke

[james03160927]

It seems like we are creating various AWS resources on cloud for unit testing. This approach works but it incurs additional cost and we see quite a lot of transient issues (e.g., QuotaLimit, Timeout, ...). We might want to try switching to this recommendation where we use mock implementation to test the behaviour we want - https://aws.amazon.com/blogs/developer/mocking-out-then-aws-sdk-for-go-for-unit-testing/.

[james03160927]

https://www.notion.so/gruntwork/Cloud-Nuke-Restructure-Proposal-845f291e952844ae8b0054ad0e466cfc