feat(ui): add collection admin config for custom debounce timeout for form updates

[taheraab]

What and Why?

Every form field change causes a (debounced) request to the server containing the form state, and the returned server state is then reconciled on the client, causing client side re-rendering.
At AMBOSS, some of our collections are large and contain multiple text and richText fields. We do not have autoSave enabled and don't have a lot of conditional UI. We'd like to tweak the debounce timeout of these form updates for two reasons.

1. The request size can be very large that puts sufficient load on our Next.js server degrading its performance and thus slowly down the application.
2. Frequent client reconciliation makes the UI laggy and unresponsive.

How?

Add a collection admin config to provide a custom debounce timeout for form updates. For example,

export const PostsCollection: CollectionConfig = {
  slug: postsSlug,
  admin: {
    useAsTitle: 'title',
    enableListViewSelectAPI: true,
    formUpdateDebounceTimeout: 500
  },
 ...

Fixes #