Upgrade to AWS Client lib v2, use new async API?

[fm3]

We use AWS Client in the S3DataVault. A v2 of the lib has been released. We should have a look at wether we can benefit from integrating it. Since we only use very few calls to this lib, the effort should be manageable.

https://github.com/aws/aws-sdk-java-v2/#using-the-sdk