[monitoring] Impl metrics

[chernser]

Summary

• Adds Sink tasks metrics
• Adds topic metrics

Sink task and topic metrics are accessible via JMX. Bean name format is com.clickhouse:type=ClickHouseKafkaConnector,name=SinkTask<taskId>,version=<version>.
For example, com.clickhouse:type=ClickHouseKafkaConnector,name=SinkTask0,version=v1.3.5.

Topic metrics bean name format is com.clickhouse:type=ClickHouseKafkaConnector,name=SinkTask<taskId>,version=<version>,topic=<topic>.
For example com.clickhouse:type=ClickHouseKafkaConnector,name=SinkTask0,version=v1.3.5,topic=schemaless_simple_batch_test_1762822854777.

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

[Copilot]

Pull Request Overview

This PR implements metrics collection and JMX monitoring capabilities for the ClickHouse Kafka connector sink tasks. The changes enable tracking of key performance indicators such as record processing rates, batch statistics, event lag times, and insert durations.

Key changes:

• Introduces JMX MBeans for exposing sink task and topic-level statistics
• Adds tracking of successful/failed records and batches, receive lag, and insert time metrics
• Updates test infrastructure to register/unregister MBeans properly in test lifecycle

Reviewed Changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
TopicStatisticsMBean.java	Defines MBean interface for topic-level metrics (success/failure counts, lag, insert time)
TopicStatistics.java	Implements topic statistics tracking using atomic counters and exponential moving averages
SinkTaskStatisticsMBean.java	Adds getInsertedRecords method to sink task MBean interface
SinkTaskStatistics.java	Enhances statistics collection with thread-safe atomics, topic-level tracking, and MBean registration
Processing.java	Integrates statistics recording for insert operations including event receive lag calculation
ClickHouseWriter.java	Records insert time metrics across all insert method variants
ProxySinkTask.java	Refactors to use final fields and handles MBean lifecycle management
ClickHouseSinkTask.java	Exposes taskId accessor for test verification
ProcessingTest.java	Updates tests to properly manage SinkTaskStatistics MBean lifecycle
ClickHouseWriterTest.java	Updates constructor calls to pass SinkTaskStatistics instances
ClickHouseSinkTaskTest.java	Adds comprehensive tests for metrics validation and mean lag time calculation

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