use read/send instead of sendfile

common/cpp/src/system_io/system_io.cpp

common/cpp/src/system_io/system_io.h

common/cpp/src/system_io/system_io_linux_mac.cpp

common/cpp/src/system_io/system_io_windows.cpp

producer/api/cpp/src/producer_request.cpp

producer/api/cpp/src/request_handler_filesystem.cpp

producer/api/cpp/src/request_handler_tcp.cpp

producer/api/cpp/unittests/test_request_handler_tcp.cpp