Refactor ExcalidrawElement (#874)

* Get rid of isSelected, canvas, canvasZoom, canvasOffsetX and canvasOffsetY on ExcalidrawElement.

* Fix most unit tests. Fix cmd a. Fix alt drag

* Focus on paste

* shift select should include previously selected items

* Fix last test

* Move this.shape out of ExcalidrawElement and into a WeakMap

src/actions/actionSelectAll.ts

@@ -3,9 +3,14 @@ import { register } from "./register";
 
 export const actionSelectAll = register({
   name: "selectAll",
-  perform: elements => {
+  perform: (elements, appState) => {
     return {
-      elements: elements.map(elem => ({ ...elem, isSelected: true })),
+      appState: {
+        ...appState,
+        selectedElementIds: Object.fromEntries(
+          elements.map(element => [element.id, true]),
+        ),
+      },
     };
   },
   contextItemLabel: "labels.selectAll",