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/composables/node/useNodeImage.ts

@@ -98,7 +98,7 @@ const useNodePreview = <T extends MediaElement>(
 /**
  * Attaches a preview image to a node.
  */
-export const useNodeImage = (node: LGraphNode) => {
+export const useNodeImage = (node: LGraphNode, callback?: () => void) => {
   node.previewMediaType = 'image'
 
   const loadElement = (url: string): Promise<HTMLImageElement | null> =>
@@ -112,6 +112,7 @@ export const useNodeImage = (node: LGraphNode) => {
   const onLoaded = (elements: HTMLImageElement[]) => {
     node.imageIndex = null
     node.imgs = elements
+    callback?.()
   }
 
   return useNodePreview(node, {
@@ -126,7 +127,7 @@ export const useNodeImage = (node: LGraphNode) => {
 /**
  * Attaches a preview video to a node.
  */
-export const useNodeVideo = (node: LGraphNode) => {
+export const useNodeVideo = (node: LGraphNode, callback?: () => void) => {
   node.previewMediaType = 'video'
   let minHeight = DEFAULT_VIDEO_SIZE
   let minWidth = DEFAULT_VIDEO_SIZE
@@ -187,6 +188,7 @@ export const useNodeVideo = (node: LGraphNode) => {
     }
 
     node.videoContainer.replaceChildren(videoElement)
+    callback?.()
   }
 
   return useNodePreview(node, {