[KIP-714] Fix for duplicate metrics when multiple prefixes are matching

[emasab]

Closes #5103

Metrics aren't duplicated when multiple prefixes match them.
Fixed by keeping track of the metrics that already matched.

[confluent-cla-assistant]

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[Copilot]

Pull Request Overview

This PR addresses the duplicate metrics issue that arises when multiple prefixes match the same metric by tracking already matched metrics. Key changes include:

• Adding a new unittest (unittest_telemetry) and updating the test mappings in rdunittest.c.
• Updating the telemetry matching logic in rdkafka_telemetry.c to prevent multiple matches via a boolean array.
• Documenting the changes in the CHANGELOG.md.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/rdunittest.c	Updated unittest mappings and added unittest_telemetry for telemetry.
src/rdkafka_telemetry.c	Implemented a boolean guard (is_metric_included) and added a new unit test.
CHANGELOG.md	Documented feature release and telemetry fixes.

Comments suppressed due to low confidence (1)

src/rdkafka_telemetry.c:177

• Verify that the size of is_metric_included is always sufficient to cover all indices up to metrics_cnt to prevent potential out-of-bounds access. Consider adding an assertion or comment clarifying the expected relationship between metrics_cnt and the array size.

rd_bool_t is_metric_included[RD_MAX((int)RD_KAFKA_TELEMETRY_PRODUCER_METRIC__CNT, (int)RD_KAFKA_TELEMETRY_CONSUMER_METRIC__CNT)] = {0};