Subgraph widget promotion fixes (#5911)

- Fixes automatic promotion of image previews by ~~more correctly
handling a usage of `requestAnimationFrame` and~~ introducing a means to
perform actions upon successful load of preview.
- When workflows contain an old proxyWidget property in string form,
parse it instead of throwing an error.
- Do not overlay the `label` of promoted widgets. Further consideration
is needed, but this resolves the primary annoyance and prevents
untranslated widget names
See #5914

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5911-Subgraph-widget-promotion-fixes-2826d73d365081838ffeeea4b8d7068c)
by [Unito](https://www.unito.io)

src/core/schemas/proxyWidget.ts

@@ -9,7 +9,10 @@ export type ProxyWidgetsProperty = z.infer<typeof proxyWidgetsPropertySchema>
 export function parseProxyWidgets(
   property: NodeProperty | undefined
 ): ProxyWidgetsProperty {
-  const result = proxyWidgetsPropertySchema.safeParse(property)
+  if (typeof property === 'string') property = JSON.parse(property)
+  const result = proxyWidgetsPropertySchema.safeParse(
+    typeof property === 'string' ? JSON.parse(property) : property
+  )
   if (result.success) return result.data
 
   const error = fromZodError(result.error)