[CSG]: Make control hints clickable

[Cloud7050]

All CSG tabs have control hints shown at their top left. These are icons that show tooltips when hovered over, explaining to the user how to interact with the canvas via mouse actions.

Some of these would make sense to also be buttons that the user can simply click, as an alternative to performing the relevant mouse action. These would be the upper 3: zoom in, zoom out, and zoom to fit. The lower 2 are rotate and pan, which do not make sense as buttons since they require dragging the mouse for a measure.