add the opentelemetry tracing (#908)

* add the opentelemetry tracing

* fix the error sampler config

* 添加stream的链路跟踪

* fix the error field name

core/opentelemetry/config.go

@@ -0,0 +1,13 @@
+package opentelemetry
+
+const (
+	TraceName = "go-zero"
+)
+
+// A Config is a opentelemetry config.
+type Config struct {
+	Name     string  `json:",optional"`
+	Endpoint string  `json:",optional"`
+	Sampler  float64 `json:",default=1.0"`
+	Batcher  string  `json:",default=jaeger"`
+}