MINOR: Fix integer overflow in LRUCacheBenchmark (#7270)

The jmh LRUCacheBenchmark will exhibit an int overflow when run on a fast machine:

```
java.lang.ArrayIndexOutOfBoundsException: Index -3648 out of bounds for length 10000
	at org.apache.kafka.jmh.cache.LRUCacheBenchmark.testCachePerformance(LRUCacheBenchmark.java:70)
	at org.apache.kafka.jmh.cache.generated.LRUCacheBenchmark_testCachePerformance_jmhTest.testCachePerformance_thrpt_jmhStub(LRUCacheBenchmark_testCachePerformance_jmhTest.java:119)
	at org.apache.kafka.jmh.cache.generated.LRUCacheBenchmark_testCachePerformance_jmhTest.testCachePerformance_Throughput(LRUCacheBenchmark_testCachePerformance_jmhTest.java:83)
```

Reviewers: Jason Gustafson <jason@confluent.io>

jmh-benchmarks/src/main/java/org/apache/kafka/jmh/cache/LRUCacheBenchmark.java

@@ -52,7 +52,7 @@ public class LRUCacheBenchmark {
 
     private LRUCache<String, String> lruCache;
 
-    int counter;
+    private long counter = 0;
 
     @Setup(Level.Trial)
     public void setUp() {
@@ -66,7 +66,7 @@ public class LRUCacheBenchmark {
     @Benchmark
     public String testCachePerformance() {
         counter++;
-        int index = counter % DISTINCT_KEYS;
+        int index = (int) (counter % DISTINCT_KEYS);
         String hashkey = keys[index];
         lruCache.put(hashkey, values[index]);
         return lruCache.get(hashkey);