fix(kafka): fix result handling when sending message with invalid header

[paulozulato]

Targeting release-52

Fixes https://emqx.atlassian.net/browse/EMQX-10846

Summary

🤖 Generated by Copilot at c2892a6

This pull request improves the Kafka bridge producer by adding instance id tracking, error handling, and code refactoring. It also fixes a bug in the GCP PubSub bridge producer that prevented boolean values in headers. It also adds a new test case for the Kafka bridge producer to verify the error handling.

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• [na] Added property-based tests for code which performs user input validation
• Changed lines covered in coverage report
• Change log has been added to changes/(ce|ee)/(feat|perf|fix)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• [na] Created PR to emqx-docs if documentation update is required, or link to a follow-up jira ticket
• [na] Schema changes are backward compatible

Checklist for CI (.github/workflows) changes

• [na] If changed package build workflow, pass this action (manual trigger)
• [na] Change log has been added to changes/ dir for user-facing artifacts update