Allow the mod assign view page to use a renderer so it can be overridden

Currently the mod assign view page does not use a renderer so it cannot be overridden
This means that the existing renderers/renderables on the page cannot be rearranged and
EXPECTED: mod assign view page to be modular, items on the page should be able to be overriden and re-arranged. e.g. I want to put the feedback into the grading table area but i cant.
ACTUAL: the view page can't be overridden in a theme at all

I am creating a suggested change that does not change existing functionality but moves the logic to a renderer and uses a view object to store all the data/logic to build the view page.