Add conditions to copy_fields processor

This commit adds conditions to the `copy_fields` processor from the
monitoring Filebeat to prevent it from failing and spamming the event
logger at debug level with:
`target field xxx already exists, drop or rename this field first`

internal/pkg/agent/application/monitoring/v1_monitor.go

@@ -424,6 +424,13 @@ func (b *BeatsMonitor) injectLogsInput(cfg map[string]interface{}, components []
 								"to":   "data_stream.dataset_original",
 							},
 						},
+						"when": map[string]any{
+							"not": map[string]any{
+								"has_fields": []any{
+									"data_stream.dataset_original",
+								},
+							},
+						},
 					},
 				},
 				// drop the dataset field so following copy_field can copy to it
@@ -443,13 +450,27 @@ func (b *BeatsMonitor) injectLogsInput(cfg map[string]interface{}, components []
 								"to":   "data_stream.dataset",
 							},
 						},
+						"when": map[string]any{
+							"not": map[string]any{
+								"has_fields": []any{
+									"data_stream.dataset",
+								},
+							},
+						},
 						"fail_on_error":  false,
 						"ignore_missing": true,
 					},
 				},
 				// possible it's a log message from agent itself (doesn't have component.dataset)
 				map[string]interface{}{
 					"copy_fields": map[string]interface{}{
+						"when": map[string]any{
+							"not": map[string]any{
+								"has_fields": []any{
+									"data_stream.dataset",
+								},
+							},
+						},
 						"fields": []interface{}{
 							map[string]interface{}{
 								"from": "data_stream.dataset_original",
@@ -471,6 +492,13 @@ func (b *BeatsMonitor) injectLogsInput(cfg map[string]interface{}, components []
 				// update event.dataset with the now used data_stream.dataset
 				map[string]interface{}{
 					"copy_fields": map[string]interface{}{
+						"when": map[string]any{
+							"not": map[string]any{
+								"has_fields": []any{
+									"event.dataset",
+								},
+							},
+						},
 						"fields": []interface{}{
 							map[string]interface{}{
 								"from": "data_stream.dataset",