KafkaSinkCluster - move destination field from PendingRequestState into PendingRequest

[alleyshairu]

This PR address #1763

It removes the destination associated field from all of the variants of the PendingRequestState enum, and moves this state to the parent type PendingRequest.

This eliminates the need to pass the destination when transitioning between states.

[CLAassistant]

All committers have signed the CLA.

[codspeed-hq]

CodSpeed Performance Report

Merging #1828 will not alter performance

_{Comparing alleyshairu:kafka_pending_request_state_destination_refactoring (6e2ee0e) with main (6a053ae)}

Summary

✅ 38 untouched benchmarks

[rukai]

Thanks, this is great!
Everything passed CI, I'll hit "Update branch" and if everything still passes we'll approve the PR.
Theres been a lot of activity in this file lately so unfortunately its not unlikely that something might break.