refactor: refactor read/write of kafka wal

[niebayes]

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What's changed and what's your intention?

• Refactor the code by introducing abstractions for Producer and Consumer functionalities.
• Migrate the buffering logic utilized by rskafka to our codebase to enhance our control over writing to Kafka.
• Each kafka record now can contain entries from multiple regions.
• Allow entries from a region to be written to Kafka out of order.
• Support fetching multiple entries from Kafka within a single Kafka record.
• Enable buffering when consuming a Kafka topic.

This PR is still in its draft version. I will add necessary tests and refine the codes.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.