SSE: (Instrumentation) Add Tracing (#66700)

spans are prefixed `SSE.`

pkg/expr/transform.go

@@ -70,6 +70,7 @@ func (s *Service) TransformData(ctx context.Context, now time.Time, req *Request
 	}
 
 	start := time.Now()
+	ctx, span := s.tracer.Start(ctx, "SSE.TransformData")
 	defer func() {
 		var respStatus string
 		switch {
@@ -80,6 +81,8 @@ func (s *Service) TransformData(ctx context.Context, now time.Time, req *Request
 		}
 		duration := float64(time.Since(start).Nanoseconds()) / float64(time.Millisecond)
 		s.metrics.expressionsQuerySummary.WithLabelValues(respStatus).Observe(duration)
+
+		span.End()
 	}()
 
 	// Build the pipeline from the request, checking for ordering issues (e.g. loops)