MM-21898: Part 2. Add opentracing (#13904)

* initial implementation of opentracing

* app layer

* Revert Makefile

* .

* cleanup

* .

* .

* .

* .

* .

* .

* .

* .

* .

* .

* .

* [ci]

* autogenerate interface

* .

* missed vendor files

* updated interfaces

* updated store layers

* lint fixes

* .

* finishing layer generators and nested spans

* added errors and b3 support

* code review

* .

* .

* fixed build error due to misplased flag.Parse()

* code review addressed

vendor/github.com/uber/jaeger-lib/metrics/timer.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2017 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metrics
+
+import (
+	"time"
+)
+
+// Timer accumulates observations about how long some operation took,
+// and also maintains a historgam of percentiles.
+type Timer interface {
+	// Records the time passed in.
+	Record(time.Duration)
+}
+
+// NullTimer timer that does nothing
+var NullTimer Timer = nullTimer{}
+
+type nullTimer struct{}
+
+func (nullTimer) Record(time.Duration) {}