…#7)

The Partition.isOneAboveMinIsr method is still defined in 3.6-li but the
gauge that exposes it as a JMX/yammer metric was lost in the PR #538
squash. Restoring matches 3.0-li ReplicaManager.scala:296. Audit also
flagged the dead-code method as P1 #8 — restoring the gauge wires it
back as the original caller.

Original 3.0-li addition: commit a2bf781 'Add metrics for log
compaction threads alive'. The gauge counts cleaner threads that are
isAlive(), complementing the already-present DeadThreadCount gauge.
Required by LI ops dashboards.

Original 3.0-li commit: 0e7ab47 'Mark FetchSession cache misses'.
The CACHE_MISSES constant and INCREMENTAL_FETCH_SESSION_CACHE_MISSES_PER_SEC
metric name were already defined in 3.6-li FetchSession companion object,
but the meter registration in FetchSessionCache and the mark() call site
on session-not-found were lost in the squash.

Restore:
- cacheMissesMeter registration in FetchSessionCache (mirrors evictionsMeter
  pattern, uses 3.6-li Collections.emptyMap() vs 3.0-li Map.empty).
- markCacheMiss() method on FetchSessionCache.
- markCacheMiss() invocation when a fetch session lookup fails (returning
  Errors.FETCH_SESSION_ID_NOT_FOUND).

Required by LI ops dashboards.

Original 3.0-li commit: b3489a1 'Add BytesInTotal & MessagesInTotal
counters'. The full counter infrastructure was lost in the PR #538
squash: the constants, CounterWrapper, counterMetricTypeMap,
accessor methods, and call sites were all gone, plus the
KafkaMetricsGroup.newCounter API itself disappeared when
KafkaMetricsGroup migrated from Scala trait to Java class
(org.apache.kafka.server.metrics).

Restore in three parts:

1. KafkaMetricsGroup (Java, server-common): add public newCounter(name)
   and newCounter(name, tags) methods that delegate to
   KafkaYammerMetrics.defaultRegistry().newCounter — mirroring the
   newGauge / newMeter API surface.

2. KafkaRequestHandler.scala (BrokerTopicMetrics + BrokerTopicStats):
   - Add CounterWrapper case class (mirrors MeterWrapper lazy-init
     pattern) using metricsGroup.newCounter.
   - Add counterMetricTypeMap[String, CounterWrapper] populated with
     MessagesInTotal and BytesInTotal at construction.
   - Add bytesInTotal and messagesInTotal accessor methods.
   - Add counterMetricMap test accessor.
   - Wire close() and closeMetric() to also close counter wrappers.
   - Add MessagesInTotal and BytesInTotal constants on BrokerTopicStats.

3. ReplicaManager.scala: at the four post-append call sites
   (per-topic + all-topics for both bytes and messages), increment
   the counter alongside the existing rate meter mark.