all: use clear() built-in Go function for clearing []prompbmarshal.TimeSeries and []prompbmarshal.Label slices

This makes the code a bit clear.

app/vmagent/common/push_ctx.go

@@ -21,13 +21,7 @@ type PushCtx struct {
 
 // Reset resets ctx.
 func (ctx *PushCtx) Reset() {
-	tss := ctx.WriteRequest.Timeseries
-	for i := range tss {
-		ts := &tss[i]
-		ts.Labels = nil
-		ts.Samples = nil
-	}
-	ctx.WriteRequest.Timeseries = ctx.WriteRequest.Timeseries[:0]
+	ctx.WriteRequest.Reset()
 
 	promrelabel.CleanLabels(ctx.Labels)
 	ctx.Labels = ctx.Labels[:0]

app/vmagent/remotewrite/pendingseries.go

@@ -122,11 +122,7 @@ func (wr *writeRequest) reset() {
 
 	wr.wr.Timeseries = nil
 
-	for i := range wr.tss {
-		ts := &wr.tss[i]
-		ts.Labels = nil
-		ts.Samples = nil
-	}
+	clear(wr.tss)
 	wr.tss = wr.tss[:0]
 
 	promrelabel.CleanLabels(wr.labels)

lib/promscrape/scrapework.go

@@ -680,11 +680,8 @@ func (wc *writeRequestCtx) reset() {
 func (wc *writeRequestCtx) resetNoRows() {
 	wc.writeRequest.Reset()
 
-	labels := wc.labels
-	for i := range labels {
-		labels[i] = prompbmarshal.Label{}
-	}
-	wc.labels = labels[:0]
+	clear(wc.labels)
+	wc.labels = wc.labels[:0]
 
 	wc.samples = wc.samples[:0]
 }

lib/protoparser/opentelemetry/stream/streamparser.go

@@ -238,13 +238,8 @@ type writeContext struct {
 func (wr *writeContext) reset() {
 	wr.bb.Reset()
 
-	tss := wr.tss
-	for i := range tss {
-		ts := &tss[i]
-		ts.Labels = nil
-		ts.Samples = nil
-	}
-	wr.tss = tss[:0]
+	clear(wr.tss)
+	wr.tss = wr.tss[:0]
 
 	wr.baseLabels = resetLabels(wr.baseLabels)
 	wr.pointLabels = resetLabels(wr.pointLabels)
@@ -254,9 +249,7 @@ func (wr *writeContext) reset() {
 }
 
 func resetLabels(labels []prompbmarshal.Label) []prompbmarshal.Label {
-	for i := range labels {
-		labels[i] = prompbmarshal.Label{}
-	}
+	clear(labels)
 	return labels[:0]
 }