Use Smaller ByteBuffers when Buffering BinaryData.fromFlux

[alzimmermsft]

Description

Use smaller ByteBuffers when buffering BinaryData.fromFlux. Smaller buffers are better as they match the original input and don't require creating large byte arrays, and prevent OOME if the Flux<ByteBuffer> size is larger than Integer.MAX_VALUE.

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• [x] The pull request does not introduce [breaking changes]
• [x] CHANGELOG is updated for new features, bug fixes or other significant changes.
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[azure-sdk]

API change check

API changes are not detected in this pull request.