fix: s3 stream pipeline ordering

[ferhatelmas]

What kind of change does this PR introduce?

Bug fix

What is the current behavior?

aws-chunked uploads (s3 streaming signature v4) could be incorrectly rejected or enforcing wrong size.

What is the new behavior?

• Reorder pipelines to decode signature first then do byte limit check. Otherwise raw body is checked, which is larger due to signature metadata.
• Prefer x-amz-decoded-content-length (actual payload size) over content-length (encoded size with chunk signatures). This prevents false EntityTooLarge errors on valid uploads.
• Replace the PassThrough no-op fallback with pipelineWithOptionalStreamingSignature, which only includes the signature transform when it exists.
• Improve test coverage.