Fix a reference leak in _io._WindowsConsoleIO: PyUnicode_FSDecoder()
always initialize decodedname when it succeed and it doesn't clear
input decodedname object.
(cherry picked from commit 29adc13bd7)
* bpo-30544: _io._WindowsConsoleIO.write raises the wrong error when WriteConsoleW fails
* bpo-30544: _io._WindowsConsoleIO.write raises the wrong error when WriteConsoleW fails
Issue #28162: WindowsConsoleIO readall() fails if first line starts with Ctrl+Z
Issue #28163: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle
Issue #28164: _PyIO_get_console_type fails for various paths