[FIX] export: image charts as base64

During the split of the model, we changed the way the image generated for charts were handled.
It worked well, except when exporting with Odoo because the zipping is done server side and the image
definition was only available server side though URL.createObjectIrl()

This fix uses the standard fileReader to obtrain a true base64 image as text, like before

closes #7439

Task: 5253880
Signed-off-by: Rémi Rahir (rar) <rar@odoo.com>

Author: VincentSchippefilt

packages/o-spreadsheet-engine/src/helpers/figures/charts/chart_ui_common.ts

@@ -127,7 +127,11 @@ async function canvasToObjectUrl(canvas: OffscreenCanvas): Promise<string | unde
   if (!blob) {
     return undefined;
   }
-  if (!URL.createObjectURL)
-    throw new Error("URL.createObjectURL is not supported in this environment");
-  return URL.createObjectURL(blob);
+  return new Promise((resolve) => {
+    const f = new FileReader();
+    f.addEventListener("load", () => {
+      resolve(f.result as string);
+    });
+    f.readAsDataURL(blob);
+  });
 }