Reintroduce multi-point arrows and add migration for it (#635)

* Revert "Revert "Feature: Multi Point Arrows (#338)" (#634)"

This reverts commit 3d2e59bfed.

* Convert old arrow spec to new one

* Remove unnecessary failchecks and fix context transform issue in retina displays

* Remove old points failcheck from getArrowAbsoluteBounds

* Remove all failchecks for old arrow

* remove the rest of unnecessary checks

* Set default values for the arrow during import

* Add translations

* fix restore using unmigrated elements for state computation

* don't use width/height when migrating from new arrow spec

Co-authored-by: David Luzar <luzar.david@gmail.com>
Co-authored-by: Christopher Chedeau <vjeuxx@gmail.com>

src/types.ts

@@ -3,6 +3,7 @@ import { ExcalidrawElement } from "./element/types";
 export type AppState = {
   draggingElement: ExcalidrawElement | null;
   resizingElement: ExcalidrawElement | null;
+  multiElement: ExcalidrawElement | null;
   // element being edited, but not necessarily added to elements array yet
   //  (e.g. text element when typing into the input)
   editingElement: ExcalidrawElement | null;