Show running time of most recent command

[ihnorton]

When working in the interactive window, I may run a cell and then do other things if I expect the evaluation to take substantial time; later I come back to check. If the call is still running after an "unreasonable" amount of time, I would likely kill it.

For the above workflow, it would be useful to have a display of the elapsed time for the most recently evaluated cell, perhaps after some minimum time has passed (maybe in place of the current spinning asterisk [*]?)

Please note that this feature request is distinct from IPython magic like %time: those work great, but they only give the elapsed time after the call has completed. I would like a timer that is independent of the kernel and shows the elapsed time since something was sent to the kernel.

[brettcannon]

Moved to https://github.com/microsoft/vscode-jupyter/issues/7378