Are things after the updater-refactoring actually still compatible with fixed_update_timer?

[johannesugb]

During the updater-refactoring, several framework-internal things have changed. Among others, imgui_manager's internal structure has changed and some code got moved from its render() to its update().

With the varying_update_timer, the order of update/render-invocations is well defined and has always a 1:1 ratio:

update();
render();
update();
render();
update();
render();

With fixed_update_timer, there is no fixed order or relation between the two. update() can be configured to run e.g. 60 times a second (i.e. fixed update rate of 60Hz), and render() is invoked as often as possible. E.g. like follows:

update();
render();
update();
update();
render();
update();
update();
render();
render();
render();
render();
update();
render();