Add snapshot S3 bucket and custome role

[gaiksaya]

Description

• Add snapshot S3 bucket that will be used to store cluster snapshots and restore relevant indices from other snapshots
• Also adds custom role with additional permissions for S3 bucket. Separating the role from the default one gave us more control on the type of policy and permissions we might want to add in future too.

Issues Resolved

List any issues this PR will resolve, e.g. Closes [...].

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license. For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[peterzhuamazon]

If already exist a bucket with same name, will it error out or skip?

[gaiksaya]

If already exist a bucket with same name, will it error out or skip?

Right! That's why it is a part of commonsStack. Had to name for easy maintenance and running curl operations.

[peterzhuamazon]

Thanks @gaiksaya , approved.