simplify wired-scene api to use constructors

spatial/wit/wired-scene/world.wit

@@ -15,7 +15,7 @@ interface material {
   }
 
   resource material {
-    id: func() -> u32;
+    constructor();
 
     name: func() -> string;
     set-name: func(value: string);
@@ -25,16 +25,12 @@ interface material {
   }
 
   list-materials: func() -> list<material>;
-  create-material: func() -> material;
-  remove-material: func(value: material);
 }
 
 interface mesh {
   use material.{material};
 
   resource primitive {
-    id: func() -> u32;
-
     material: func() -> option<material>;
     set-material: func(value: option<borrow<material>>);
 
@@ -45,7 +41,7 @@ interface mesh {
   }
 
   resource mesh {
-    id: func() -> u32;
+    constructor();
 
     name: func() -> string;
     set-name: func(value: string);
@@ -56,8 +52,6 @@ interface mesh {
   }
 
   list-meshes: func() -> list<mesh>;
-  create-mesh: func() -> mesh;
-  remove-mesh: func(value: mesh);
 }
 
 interface node {
@@ -67,7 +61,7 @@ interface node {
   use wired:physics/types.{collider, rigid-body};
 
   resource node {
-    id: func() -> u32;
+    constructor();
 
     name: func() -> string;
     set-name: func(value: string);
@@ -95,6 +89,4 @@ interface node {
   }
 
   list-nodes: func() -> list<node>;
-  create-node: func() -> node;
-  remove-node: func(value: node);
 }