feat(editor): unify block props api (#10888)

Closes: [BS-2707](https://linear.app/affine-design/issue/BS-2707/统一使用props获取和更新block-prop)

blocksuite/affine/model/src/blocks/paragraph/paragraph-model.ts

@@ -53,9 +53,7 @@ export const ParagraphBlockSchemaExtension =
   BlockSchemaExtension(ParagraphBlockSchema);
 
 export class ParagraphBlockModel extends BlockModel<ParagraphProps> {
-  override text!: Text;
-
   override isEmpty(): boolean {
-    return this.text$.value.length === 0 && this.children.length === 0;
+    return this.props.text$.value.length === 0 && this.children.length === 0;
   }
 }