feat: opentelemetry integration, removed self designed tracing (#1111)

* feat: opentelemetry integration, removed self designed tracing

* feat: support zipkin on opentelemetry integration

* feat: support zipkin on opentelemetry integration, enable it in conf

* style: format code

* fix: support logx without exporter configured

* fix: check return values

* refactor: simplify code

* refactor: simplify opentelemetry integration

* ci: fix staticcheck errors

core/trace/vars.go

@@ -0,0 +1,8 @@
+package trace
+
+import "net/http"
+
+// TraceIdKey is the trace id header.
+// https://www.w3.org/TR/trace-context/#trace-id
+// May change it to trace-id afterwards.
+var TraceIdKey = http.CanonicalHeaderKey("x-trace-id")