[chore] update otel libraries (#3740)

* chore: update otel dependencies

* refactor: combine tracing & metrics in observability package

* chore: update example tracing compose file

vendor/google.golang.org/grpc/internal/balancer/gracefulswitch/config.go

@@ -33,6 +33,8 @@ type lbConfig struct {
 	childConfig  serviceconfig.LoadBalancingConfig
 }
 
+// ChildName returns the name of the child balancer of the gracefulswitch
+// Balancer.
 func ChildName(l serviceconfig.LoadBalancingConfig) string {
 	return l.(*lbConfig).childBuilder.Name()
 }