The lack of icon gizmo made it no longer possible to select Camera3D
nodes in the 3D viewport by clicking on them.
A new Camera3D icon gizmo was designed to be direction-neutral.
This avoids the issue that the previous icon gizmo had, since it was
always facing right.
This also adds icons for CameraAttributesPractical and CameraAttributesPhysical.
Hugo Locurcio