[KIP-714] Fix: Metric name from the protocol is read outside boundaries

[emasab]

Closes #5102

Avoid copy outside boundaries when reading metric names in telemetry subscription. It can cause that some metrics aren't matched.

[confluent-cla-assistant]

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[Copilot]

Pull Request Overview

This PR ensures metric names in telemetry subscriptions are duplicated within their defined length boundaries and adds a unit test for the related handler.

• Replace unbounded rd_strdup with RD_KAFKAP_STR_DUP to avoid out-of-bounds copies of metric names.
• Introduce unittest_handle_GetTelemetrySubscriptions to validate subscription parsing.
• Update CHANGELOG.md with the new fix under v2.11.0.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/rdkafka_request.c	Swap rd_strdup for RD_KAFKAP_STR_DUP and add a unit test case.
CHANGELOG.md	Add v2.11.0 entry describing the boundary-copy fix.

Comments suppressed due to low confidence (3)

CHANGELOG.md:5

• Replace the placeholder "(#)" with the actual PR or issue number to create a proper link in the changelog.

* Avoid copy outside boundaries when reading metric names in telemetry

src/rdkafka_request.c:7001

• The assertion message uses "compression type" in singular for a count of two; consider changing it to "compression types" for clarity.

RD_UT_ASSERT(rk->rk_telemetry.accepted_compression_types_cnt == 2,

src/rdkafka_request.c:6987

• Consider adding a test case where a metric name exceeds its declared length to verify RD_KAFKAP_STR_DUP properly truncates or rejects out-of-bounds input.

rd_kafka_buf_write_arraycnt(rkbuf, 2); /* #RequestedMetrics */