Allow checking specific Eshell handles for interactive output

Allow checking specific Eshell handles for interactive output

This changes the default behavior of the function to check only stdout
for interactivity, but for most cases this should be what we want.

* lisp/eshell/esh-io.el (eshell-interactive-output-p): Pass HANDLES
and handle INDEX.

* lisp/eshell/em-term.el (eshell-visual-command-p): Check for
interactivity of both stdout and stderr.