refactor: rename 'renderer_bbox' file to 'renderer_boundingbox'

[mohamedAdhamc]

I have always thought this would just make it much clearer for newcomers looking through the code-base. I mean other renderers are called "renderer_bonedeformarea" so i don't really think length is really the issue here but this way I feel it's much cleaner.

Now if necessary I can also rename the class itself too but I think it would be cleaner to do it in another PR.