refactor(editor): optimize pasting process of attachments and images (#12276)

Related to: [BS-3146](https://linear.app/affine-design/issue/BS-3146/import-paste-接口改进优化)

blocksuite/affine/components/src/resource/resource.ts

@@ -35,6 +35,7 @@ export type ResolvedStateInfo = StateInfo & ResolvedStateInfoPart;
 export class ResourceController implements Disposable {
   readonly blobUrl$ = signal<string | null>(null);
 
+  // TODO(@fundon): default `loading` status.
   readonly state$ = signal<Partial<BlobState>>({});
 
   readonly resolvedState$ = computed<ResolvedStateInfoPart>(() => {