Add benchmark metric test for UpDownCounter (#2655)
Add benchmark metric test for UpDownCounter (#2655)

* add benchmark metric test for UpDownCounter

* move counter annotation up

* fix syncFloat64 to syncInt64

* fix syncFloat64 to syncInt64

* fix go-lint err
open-telemetry/opentelemetry-go,open-telemetry/opentelemetry-go