gh-139349: fix init dataclass Console init with value ignore repr error

[yihong0618]

init it with default value to avoid repr error

• Issue: print _pyrepl.readline._wrapper.reader will raise error'UnixConsole' object has no attribute 'posxy' #139349

[picnixz]

I don't think we should use Console before prepare() has been called. Thus, this should likely not be fixed like that.

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[picnixz]

All the console interface is a private implementation detail (_pyrepl is private and _pyrepl.readline._wrapper.reader is even more private, so no one should directly access it; if one incorrectly uses UnixConsole(), then something wrong may happen). I am still unconvinced that we should do anything here. I'll let @pablogsal or @ambv decide on the course of action here (though just removing console from the repr might be fine; however no NEWS should be added IMO).