Use aws-sdk-v1 instead of aws-sdk gem.

The intent of this PR is to make it possible for `v1` and `v2` of the `aws-sdk` gem to be used at the same time ([reference](https://github.com/aws/aws-sdk-core-ruby#using-v1-and-v2-together)).

I'm working on another PR that needs to use `v2`. I noticed that the `code_deploy` provider requires `aws-sdk-core`, which isn't in the Gemfile. To be more explicit I updated that dependency.