Add CliCredentials, config_grpc_cli.h

Makefile

build.yaml

test/cpp/util/cli_credentials.cc

test/cpp/util/cli_credentials.h

test/cpp/util/config_grpc_cli.h

test/cpp/util/grpc_cli.cc

test/cpp/util/grpc_tool.cc

test/cpp/util/grpc_tool.h

test/cpp/util/grpc_tool_test.cc

test/cpp/util/proto_file_parser.cc

test/cpp/util/proto_file_parser.h

test/cpp/util/proto_reflection_descriptor_database.cc

tools/run_tests/sources_and_headers.json

vsprojects/vcxproj/grpc_cli_libs/grpc_cli_libs.vcxproj

...jects/vcxproj/grpc_cli_libs/grpc_cli_libs.vcxproj.filters