feat(editor): replace spec provider with extension manager (#11861)

Closes: BS-3273

blocksuite/integration-test/src/view.ts

@@ -0,0 +1,7 @@
+import { ViewExtensionManager } from '@blocksuite/affine/ext-loader';
+import { MigratingViewExtension } from '@blocksuite/affine/extensions/view';
+
+export function getTestViewManager() {
+  const manager = new ViewExtensionManager([MigratingViewExtension]);
+  return manager;
+}