Fix uio.TextIOWrapper() behavior

[pfalcon]

Currently, it has constructor uio.TextIOWrapper(filename). Instead, it should be uio.TextIOWrapper(stream): https://docs.python.org/3/library/io.html#io.TextIOWrapper

Current situation effectively means that there's no way to convert a binary stream to text stream (socket has a workaround using .makefile() method).

[pfalcon]

io.TextIOWrapper is explicitly documented as buffered stream in CPython docs. As supporting buffered text streams is a separate issue, it was decided to implement needed functionality on the level of uio.TextIOBase. In CPython, it's an abstract base class, but we recast it as a generic, unbuffered adapter from binary to text streams.

So, now it's possible to do uio.TextIOBase(uio.BytesIO(b"1234")).

This change is made so far to the unix port, other ports need to catch up with it later. (For now, they keep using old uio.TextIOWrapper, so it's left in the codebase.)