[JS] Move io operations to arrow.io namespace

[asfimport]

Maybe create separate arrow.io.file and arrow.io.stream objects?

Reporter: Brian Hulette / @TheNeuralBit

Related issues:

• [JS] Implement JavaScript-compatible implementation (Is contained by)

_{Note: This issue was originally created as ARROW-870. Please see the migration documentation for further details.}

[asfimport]

Brian Hulette / @TheNeuralBit:
No longer relevant with the new js library.