chore: Clean up resources in gRPCStreamDirectController and ChannelPool tests#1691

lqiu96 merged 11 commits intomaingoogleapis/sdk-platform-java:mainfrom

main-fix-grpcstreamdirectcontroller_flaky_testgoogleapis/sdk-platform-java:main-fix-grpcstreamdirectcontroller_flaky_testCopy head branch name to clipboard