Change getPage() to be StatelessWidget

[hoffmannkrzysztof]

While checking the code. I noticed that there is a function that returns Widget. It should not be like that. If you do, it is a performance issue as this widget cannot be reused in the widget tree and it is rebuilt every time. Its better to replace getPage() to StatelessWidget with two parameters: bool firstLoad, WorkoutData workoutData and use ThemeProvider internally.

[jorre127]

Agree with this, I avoid using functions that return widgets as much as possible, definitely something to keep in mind when we rewrite this page.