Add 'on_demand' option to interact() so that long-running functions can be started only when explicitly requested
Disable run button until the function finishes
Add tests for the on_demand option
Merge master
Change from on_demand kwarg to interact_choose function
s/choose/manual/g
Add docs/source/whatsnew/pr/interact-manual.rst
Merge pull request #6051 from chronitis/interact-widget-on-demand

Interact on_demand option