Add control for managing framebuffer clearing

[Archez]

This adds the ability to decide whether to clear color or depth data (or both) on a framebuffer.

Prior to #607 we always cleared both. After #607 we only were clearing depth data. This had a negative impact on the "main" framebuffer used for rendering imgui where artifacts were preserved. This would appear whenever the game render space was not identical to the main window (like when using advanced resolution features).

With ability to clear things independently, we can now ensure that the main framebuffer is always cleared if the game is not rendered to it. This should resolve issues with the advanced resolution editor, without reverting anything needed by #607