Add a Shutdown method to sdk TraceProvider (#1227)

* Add a Shutdown method to api TraceProvider

- sdktraceprovider shutdown span processors
- In examples, replace processosr shutdown with
  traceprovider's shutdown

Signed-off-by: Hui Kang <kangh@us.ibm.com>

* remove shutdown in the api provider interface

* Add context in parameter and return error

* handle error in shutdown

* Update CHANGELOG.md

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

example/basic/main.go

@@ -46,8 +46,8 @@ func main() {
 	}
 
 	bsp := sdktrace.NewBatchSpanProcessor(exporter)
-	defer bsp.Shutdown()
 	tp := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(bsp))
+	defer func() { _ = tp.Shutdown(context.Background()) }()
 	pusher := push.New(
 		basic.New(
 			simple.NewWithExactDistribution(),