batchRetries to countersWithHost (grafana#7392)

**What this PR does / why we need it**:
Metric promtail_batch_retries_total is absent when has value == 0

**Which issue(s) this PR fixes**:
Fixes grafana#7261

clients/pkg/promtail/client/client.go

@@ -94,7 +94,7 @@ func NewMetrics(reg prometheus.Registerer, streamLagLabels []string) *Metrics {
 	}, []string{HostLabel})
 
 	m.countersWithHost = []*prometheus.CounterVec{
-		m.encodedBytes, m.sentBytes, m.droppedBytes, m.sentEntries, m.droppedEntries,
+		m.encodedBytes, m.sentBytes, m.droppedBytes, m.sentEntries, m.droppedEntries, m.batchRetries,
 	}
 
 	streamLagLabelsMerged := []string{HostLabel, ClientLabel}