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 8e73bab9.

This reverts commit 5b3dc525.

This reverts commit 1f173184.