Start building out AWS utility functions for CLIs, with aws-sdk-go-v2

[yorinasub17]

I am starting to build out a new CLI for a hackday project, and in the process I realized that we don't have a central library for AWS access in production CLIs (resulting in duplication: e.g., see refarch-deployer and kubergrunt). This is the start of building out a common aws helper library for use in CLIs.

In addition, aws-sdk-go v2 is now out. We should start to slowly transition to using the v2 line, as I expect v1 to be deprecated soon.

In that regard, I propose we:

• Start to build out common AWS functionality here.
• For new CLI tools that interact with AWS, use go-commons' aws interface as much as possible.
• Implicitly, new CLI tools should use aws-sdk-go-v2.
• In ticket jam, slowly upgrade existing tools to switch to aws-sdk-go-v2. For common libraries like terratest, this should be done by adding a v2 folder (and drop v1 when we reach parity). Note that this should be done in parallel with the switch to go-commons.

This PR is the start of that.

[yorinasub17]

Thanks for review! Merging this in!