Merge branch 'master' into worker_quit

Makefile

build.yaml

src/csharp/Grpc.Core/Internal/PlatformApis.cs

src/csharp/Grpc.Core/Internal/UnmanagedLibrary.cs

src/proto/grpc/testing/control.proto

src/proto/grpc/testing/services.proto

test/cpp/qps/client.h

test/cpp/qps/client_async.cc

test/cpp/qps/driver.cc

test/cpp/qps/limit_cores.cc

test/cpp/qps/limit_cores.h

test/cpp/qps/qps-sweep.sh

test/cpp/qps/qps_driver.cc

test/cpp/qps/qps_worker.cc

test/cpp/qps/server.h

tools/run_tests/sources_and_headers.json

vsprojects/vcxproj/qps/qps.vcxproj

vsprojects/vcxproj/qps/qps.vcxproj.filters