Update Icons

Subdivided the new icons in 3 size categories. As requested by UX
Used the company naming scheme for uniformity and easy recognition.

Known issues:
- Top/Bottom category wasn't taken into account by UX at the time. Since
 this is a recent addition. Both the Walls and Top/Bottom will be updated.
- Cloud/Network connection icons 12px don't render correctly. Due to the
 theme-ing.
- Extruder Icons do not render correctly.

CURA-8010_new_icons

plugins/SimulationView/SimulationViewMenuComponent.qml

@@ -203,7 +203,7 @@ Cura.ExpandableComponent
                     anchors.right: extrudersModelCheckBox.right
                     width: UM.Theme.getSize("layerview_legend_size").width
                     height: UM.Theme.getSize("layerview_legend_size").height
-                    source: UM.Theme.getIcon("extruder_button")
+                    source: UM.Theme.getIcon("Extruder", "30")
                     color: model.color
                 }