tfdbg: allow CLI to display feed values
tfdbg: allow CLI to display feed values

Also updates programmer_guide/debugger.md

RELNOTES: TensorFlow Debugger (tfdbg) CLI: added ability to display feed_dict values to Session.run through the "pf" / "print_feed" command and clickable links in the curses UI.
PiperOrigin-RevId: 162648456

tensorflow/docs,tensorflow/docs,tensorflow/docs-l10n,tensorflow/docs