HPCC-XXXXX Add S3 direct API storage plane support

[giftyedwin1]

Add S3 storage plane support via the file hook mechanism, enabling Thor and Roxie to read/write S3 objects transparently through the IFile/IFileIO interfaces.

Core implementation:

• S3FileReadIO: read via HTTP GET with Range headers
• S3FileWriteIO: buffered writes with automatic PutObject (<8MB) or multipart upload (>=8MB) selection
• S3MultipartUpload: manages CreateMultipartUpload/UploadPart/Complete lifecycle with abort-on-destroy safety
• S3File: IFile implementation with metadata caching, directory listing via ListObjectsV2
• S3APICopyClient: server-side copy for files <=5GB, multipart copy for larger files
• Retry with exponential backoff and jitter for all S3 operations
• S3 client cache keyed by storage plane name and device number

Platform changes:

• Add queryPlaneName() to IStorageApiInfo interface
• Add S3 bucket/region/endpoint config to storage plane schema
• Add jplane_compat.hpp shim for cross-version jlib compatibility
• Update Helm template validation to accept buckets (S3) or containers (Azure)

Deployment:

• Dockerfile overlay for building S3 hook against stock platform-core
• Helm values examples for S3 on EKS with IRSA authentication
• Build and deployment guide (helm/examples/s3/README.md)

Testing:

• ECL integration test verifying putObject vs multipart upload paths
• Unit tests for S3 URL validation

Type of change:

• This change is a bug fix (non-breaking change which fixes an issue).
• This change is a new feature (non-breaking change which adds functionality).
• This change improves the code (refactor or other change that does not change the functionality)
• This change fixes warnings (the fix does not alter the functionality or the generated code)
• This change is a breaking change (fix or feature that will cause existing behavior to change).
• This change alters the query API (existing queries will have to be recompiled)

Checklist:

• My code follows the code style of this project.
  • My code does not create any new warnings from compiler, build system, or lint.
• The commit message is properly formatted and free of typos.
  • The commit message title makes sense in a changelog, by itself.
  • The commit is signed.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly, or...
  • I have created a JIRA ticket to update the documentation.
  • Any new interfaces or exported functions are appropriately commented.
• I have read the CONTRIBUTORS document.
• The change has been fully tested:
  • I have added tests to cover my changes.
  • All new and existing tests passed.
  • I have checked that this change does not introduce memory leaks.
  • I have used Valgrind or similar tools to check for potential issues.
• I have given due consideration to all of the following potential concerns:
  • Scalability
  • Performance
  • Security
  • Thread-safety
  • Cloud-compatibility
  • Premature optimization
  • Existing deployed queries will not be broken
  • This change fixes the problem, not just the symptom
  • The target branch of this pull request is appropriate for such a change.
• There are no similar instances of the same problem that should be addressed
  • I have addressed them here
  • I have raised JIRA issues to address them separately
• This is a user interface / front-end modification
  • I have tested my changes in multiple modern browsers
  • The component(s) render as expected

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Testing: