feat: save body and occurrence visibility with the design (#531) (#592)

Hidden bodies, occurrence placements, sketches and origin items are saved with the design and come back when it is reopened. Visibility is still not an undo step, but hiding or showing something now counts as an unsaved change. Additive field under format 16. Fixes #531.

Co-authored-by: jonaswre <jonas.wrede@beyondit.gmbh>

crates/engine/src/cmd/browser.rs

@@ -36,7 +36,7 @@ pub static COMMANDS: &[CommandSpec] = &[
     CommandSpec::new("browser.order", "Order Browser Items", order).params("folder, component?, order: [keys] (the folder's items in display order)"),
     CommandSpec::new("browser.visibility", "Show/Hide", visibility).icon("eye").noundo().params(
         "visible: bool; items?: [sketch id or name | body name | construction name | O|X|Y|Z|XY|XZ|YZ]; \
-         or folder?: bodies|sketches|construction|origin (all of it); or paths?: [[occurrence ids]] (exact placements and descendants), isolate?: bool (requires paths and visible:true). View state: not saved, not an undo step",
+         or folder?: bodies|sketches|construction|origin (all of it); or paths?: [[occurrence ids]] (exact placements and descendants), isolate?: bool (requires paths and visible:true). Saved with the design; not an undo step",
     ),
 ];