MINOR: Delete unused class, LogOffsetMetadata toString formatting (#14246)

Noticed that there was a dangling unused class (LongRef, replaced by PrimitiveRef.LongRef), and the LogOffsetMetadata toString was a little oddly formatted.

Reviewers: Justine Olshan <jolshan@confluent.io>

core/src/main/scala/kafka/common/LongRef.scala

@@ -1,61 +0,0 @@
-/**
-  * Licensed to the Apache Software Foundation (ASF) under one or more
-  * contributor license agreements.  See the NOTICE file distributed with
-  * this work for additional information regarding copyright ownership.
-  * The ASF licenses this file to You under the Apache License, Version 2.0
-  * (the "License"); you may not use this file except in compliance with
-  * the License.  You may obtain a copy of the License at
-  *
-  *    http://www.apache.org/licenses/LICENSE-2.0
-  *
-  * Unless required by applicable law or agreed to in writing, software
-  * distributed under the License is distributed on an "AS IS" BASIS,
-  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  * See the License for the specific language governing permissions and
-  * limitations under the License.
-  */
-
-package kafka.common
-
-/**
-  * A mutable cell that holds a value of type `Long`. One should generally prefer using value-based programming (i.e.
-  * passing and returning `Long` values), but this class can be useful in some scenarios.
-  *
-  * Unlike `AtomicLong`, this class is not thread-safe and there are no atomicity guarantees.
-  */
-class LongRef(var value: Long) {
-
-  def addAndGet(delta: Long): Long = {
-    value += delta
-    value
-  }
-
-  def getAndAdd(delta: Long): Long = {
-    val result = value
-    value += delta
-    result
-  }
-
-  def getAndIncrement(): Long = {
-    val v = value
-    value += 1
-    v
-  }
-
-  def incrementAndGet(): Long = {
-    value += 1
-    value
-  }
-
-  def getAndDecrement(): Long = {
-    val v = value
-    value -= 1
-    v
-  }
-
-  def decrementAndGet(): Long = {
-    value -= 1
-    value
-  }
-
-}

storage/src/main/java/org/apache/kafka/storage/internals/log/LogOffsetMetadata.java

@@ -80,7 +80,7 @@ public final class LogOffsetMetadata {
 
     @Override
     public String toString() {
-        return "(offset=" + messageOffset + "segment=[" + segmentBaseOffset + ":" + relativePositionInSegment + "])";
+        return "(offset=" + messageOffset + ", segment=[" + segmentBaseOffset + ":" + relativePositionInSegment + "])";
     }
 
     @Override