This PR ensures that all 3 ways of handling key events are wrapped with exception handling logic, so that user exceptions do not cause unstable states and are correctly reported.

* Added a generic tooltip widget

* added the header

* finished dropdown widget

* removed mock state

* Added step 1 substeps

* stepper tests fail

* tests still fail

* removed redundant checkbox

* removed test data

* full fixes based on Chris' comments

* changed widget's name

* changed statefulwidget, added test

* fixes based on Casey's comments

* empty commit to kick pending checks

This reverts commit 31e33647.

This change updates the platform runners in the benchmarks subdir.

I've attempted to replace the entire group with new code as if the project were recreated with flutter create so that they don't become a Frankenstein of minor changes to make it work again, but just plain old generated code that can be replaced and updated in place.

This reverts commit 6b94f2f6.