Is your feature request related to a problem? Please describe.
Current s3 scan does not support bucket cross regions with iam credential:

version: "2"
log-pipeline:
  source:
    s3:
      codec:
        newline: # Other options "json", "csv", "parquet"
      compression: "none"
      aws:
        region: "us-east-1"
        sts_role_arn: "arn:aws:iam::253613578708:role/FullAccess"
      scan:
        buckets:
          - bucket:
              name: "test-s3-gd-bucket" # bucket in us-west-2

Describe the solution you'd like
user should be allowed to configure region for each bucket in the buckets list.

Describe alternatives you've considered (Optional)
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.