Remove 'onFilteredOut' and 'onDroppedOnPublish' callback logs (#36399)

The 'onFilteredOut' and 'onDroppedOnPublish' callbacks debug logs can
cause an infinity loop of log entries being logged over and over again
when running under Elastic-Agent. Those log entries are removed to
prevent this from happening in the future.

The monitoring Filebeat uses a drop processor to drop its own logs,
however if log level is debug the `onFilteredOut` callback debug log
will log all dropped events, because it is done by the monitoring
Filebeat, it will be picked up, dropped and logged again, creating
this infinity loop.

CHANGELOG.next.asciidoc

@@ -101,6 +101,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Remove erroneous error log in GCPPubSub input. {pull}36296[36296]
 - Fix Filebeat Cisco module with missing escape character {issue}36325[36325] {pull}36326[36326]
 - Fix panic when redact option is not provided to CEL input. {issue}36387[36387] {pull}36388[36388]
+- Remove 'onFilteredOut' and 'onDroppedOnPublish' callback logs {issue}36299[36299] {pull}36399[36399]
 
 *Heartbeat*
 

libbeat/publisher/pipeline/client.go

@@ -203,12 +203,10 @@ func (c *client) onPublished() {
 }
 
 func (c *client) onFilteredOut(e beat.Event) {
-	c.logger.Debugf("Pipeline client receives callback 'onFilteredOut' for event: %+v", e)
 	c.observer.filteredEvent()
 }
 
 func (c *client) onDroppedOnPublish(e beat.Event) {
-	c.logger.Debugf("Pipeline client receives callback 'onDroppedOnPublish' for event: %+v", e)
 	c.observer.failedPublishEvent()
 	if c.clientListener != nil {
 		c.clientListener.DroppedOnPublish(e)