RFR: 8209937: Enhance java.io.Console - provide methods to query console width and height

[Martin Buchholz]

History: I was always a little disappointed that Console (understandably)
didn't support the things you could do with subprocesses in Emacs, like
implement shell buffers and otherwise have expect-style conversations with
subprocesses.  But console dimensions was never on my radar - doesn't mean
much in an Emacs shell buffer.  Being able to reimplement Emacs in pure
Java is of course the ever elusive Holy Grail.  Of course, when I run java,
it's usually living inside a shell buffer.