[v2] Enhancements for CRT S3 integration

[hssyoo]

• Support the following S3 config options when using the CRT client:
  • max_attempts
  • multipart_threshold
  • max_concurrent_requests
• Support automatically following region redirect errors when using the CRT client
• For hosts that will automatically resolve to using the CRT client in the future, set defaults to minimize peak memory and preserve backwards compatibility
• Emit warnings when resolved transfer client doesn't support user-configured options