profvis of shinytest

[harrismcgehee]

Feature request:
profvis::profvis(shiny::runApp()) gives a source code view on the Flame graph after manually interacting with the app.

profvis::profvis(shinytest::testApp(interactive = FALSE)) doesn't give a source code view or much help in diagnosing the code that is running long, but it would provide a nice way to reproducibly profile many parts of a large shiny app.

Feel free to move to shinytest if the feature belongs there. Thanks!