Release v1.38.0 (googleapis#655)

Release v1.37.0 (googleapis#646)

Shutdown GRPC managed channel properly on close (googleapis#628)

Fix #3912, 3693 & 3648 Shutdown GRPC Managed channel properly on closing of background resources.

Release gax-java v1.35.1 (googleapis#624)

Release v1.35.0 (googleapis#617)

Release v1.34.0 (googleapis#611)

release 1.33.1/0.50.1 (googleapis#596)

* release 1.33.1/0.50.1

release 1.33.0/0.50.0 (googleapis#586)

Stage release 1.32.0/0.49.0 (googleapis#577)

Stage release 1.31.0/0.48.0 (googleapis#574)

Stage release 1.31.0/0.48.0