feat: [CI-16855]: Fix S3 authentication to properly handle combined credential methods and role assumption

[Ompragash]

Summary

The current implementation of the S3 client creation doesn't correctly handle scenarios where both primary credentials (access/secret keys, web identity, or initial role assumption) and secondary role assumption (via UserRoleArn) are used together. This causes authentication failures when users need to authenticate with one method and then assume a different role for S3 operations.

Solution

Refactor createS3Client method to properly chain authentication methods:

1. First establish primary credentials (static credentials, web identity tokens, or initial role assumption)
2. Create an authenticated session with those credentials
3. If UserRoleArn is provided, use that authenticated session to assume the secondary role
4. Preserve all configuration options (endpoint, path style, region, etc.) when creating the final client

Verification

The solution has been verified to work across all target environments:

IRSA Environment: Successful execution
Regular Kubernetes: Successful execution
Cloud Build: Successful execution