### What?
Optimize the `RelationshipProvider` to only select the `useAsTitle`
field when fetching documents via the REST API. This reduces payload
size and speeds up loading of the related document title in
the`RelationshipCell` in the table view.
### Why?
Previously, when a document had a relationship field, the full document
data was requested in the table view, even though the relationship cell
only shows the title in the UI. On large collections, this caused
unnecessary overhead and slower UI performance.
### How?
Applies a select to the REST API request made in the
`RelationshipProvider`, limiting the responses to the `useAsTitle` field
only.
### Notes
- I’m not entirely sure whether this introduces a breaking change. If it
does, could you suggest a way to make this behavior opt-in?
- For upload enabled collections, the full document must be requested,
because the relationship cell needs access to fields like `mimeType`,
`thumbailURL` etc.
- I hope we can find a way to get this merged. In the Payload projects I
work on, this change has significantly improved list view performance.
Similar to #13228
77cac30046