feat: upgrade Confluent.Kafka.* to 2.13.2 for native ARM64/Alpine support

[chrborg]

Description

This PR upgrades all Confluent.Kafka and Confluent.SchemaRegistry‑related dependencies across the repository to version 2.13.2, which includes native ARM64 and Alpine (musl) support through updated librdkafka bindings.

The previous versions (2.8.0) did not ship ARM64 or Alpine‑compatible native libraries, causing runtime failures such as:

System.DllNotFoundException: Failed to load the librdkafka native library

Additionally, due to changes to the Protobuf perf serialization improvements, TestProtoMessage.cs was also regenerated to confirm to latest standard and ultimately fixing integration test which broke as a result.

Fixes # (issue)

How Has This Been Tested?

• Packaged local Kafkaflow nugets and installed them in a custom app built on ARM64 Alpine containers to validate native library loading.
• Verified producer/consumer flows using the updated Confluent client.
• Ran unit and integration tests contained in the repo.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have made corresponding changes to the documentation

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