[release-2.1] fix: the rawType of Content was not updated when switching editors (#910)

This is an automated cherry-pick of #904

/assign JohnNiang

```release-note
修复在新建文章时，首次切换编辑器后没有设置内容 rawType 资源为对应编辑器类型的问题。
```

src/modules/contents/pages/SinglePageEditor.vue

@@ -48,6 +48,7 @@ const handleChangeEditorProvider = (provider: EditorProvider) => {
   formState.value.page.metadata.annotations = {
     "content.halo.run/preferred-editor": provider.name,
   };
+  formState.value.content.rawType = provider.rawType;
 };
 
 // SinglePage form

src/modules/contents/posts/PostEditor.vue

@@ -48,6 +48,7 @@ const handleChangeEditorProvider = (provider: EditorProvider) => {
   formState.value.post.metadata.annotations = {
     "content.halo.run/preferred-editor": provider.name,
   };
+  formState.value.content.rawType = provider.rawType;
 };
 
 // Post form