KAFKA-19753: Fix duplicated topic metrics in FetchMetricsManager for topic names containing dots

[wilmerdooley]

Since 4.1.0, FetchMetricsManager registers the KIP-1109 deprecated metrics (topic names with dots replaced by underscores) alongside the new verbatim-name metrics. The deprecated names were derived by string-wrapping the new-format metric name, which produced colliding and duplicated sensors when a consumer subscribes to topics whose names differ only by dots versus underscores (for example my.topic and my_topic), and left stale deprecated sensors registered when they should no longer be reported. Users scraping these metrics through Micrometer or Prometheus saw duplicated topic-tagged series.

This change:

• Derives the deprecated metric and sensor names through dedicated deprecated*MetricName helpers based on the mangled (dot-to-underscore) topic name, instead of wrapping the new-format name.
• Registers a deprecated sensor only when it does not collide with the sensor of a real topic whose name equals the mangled name, covering both registration orders (dotted topic seen first, underscore topic seen first).
• Adds maybeRemoveDeprecated* cleanup so deprecated sensors and metrics are unregistered once they should no longer be reported, including during assignment updates, with collision-aware removal so a still-assigned partition's metrics are never dropped.

The deprecated metrics themselves remain in place for topics with dots, as intended by KIP-1109, until their removal in Kafka 5.0.

Testing: five new unit tests in FetchMetricsManagerTest cover the dotted-versus-underscore topic interplay in both registration orders, topics without dots (no deprecated sensor registered), the partition-level lag/lead/preferred-read-replica metrics, and assignment updates. Verified with the scoped module run ./gradlew :clients:test --tests org.apache.kafka.clients.consumer.internals.FetchMetricsManagerTest.

JIRA: https://issues.apache.org/jira/browse/KAFKA-19753