Support aws login source_profile role chains

[rayzorinc]

Changes

This updates the AWS SDK to v2 so cli53 can work with profiles sourced from aws login, including role assumption profiles that use source_profile.

This is needed so commands like cli53 list --profile foo can resolve credentials correctly with the newer login-based workflow.

Without it, it was silently failing, but adding a debug output it would return the following error:

 unable to load AWS SDK config: failed to load assume role arn:aws:iam::xxx:role/xxxx, of profile default

Reference:

https://aws.amazon.com/blogs/security/simplified-developer-access-to-aws-with-aws-login/

Verification:

• go test ./...
• verified list --profile foo --format json with a login-backed role profile"