kgo: change default MaxBufferedRecords from unlimited to 10,000

10k was the original limit. I'm not sure when this was bumped to
unlimited, but it is problematic when producing to topics that do not
exist. 10k is still a good limit.

pkg/kgo/config.go

@@ -451,7 +451,7 @@ func defaultCfg() cfg {
 		acks:                AllISRAcks(),
 		compression:         []CompressionCodec{SnappyCompression(), NoCompression()},
 		maxRecordBatchBytes: 1000000, // Kafka max.message.bytes default is 1000012
-		maxBufferedRecords:  math.MaxInt64,
+		maxBufferedRecords:  10000,
 		produceTimeout:      30 * time.Second,
 		recordRetries:       math.MaxInt64,             // effectively unbounded
 		partitioner:         StickyKeyPartitioner(nil), // default to how Kafka partitions
@@ -859,7 +859,7 @@ func ProducerBatchMaxBytes(v int32) ProducerOpt {
 
 // MaxBufferedRecords sets the max amount of records the client will buffer,
 // blocking produces until records are finished if this limit is reached.
-// This overrides the unbounded default.
+// This overrides the default of 10,000.
 func MaxBufferedRecords(n int) ProducerOpt {
 	return producerOpt{func(cfg *cfg) { cfg.maxBufferedRecords = int64(n) }}
 }