fix: trashed documents still show as IDs in relationship responses (#16102)

# Overview

When a relationship points to a collection with `trash: true`,
soft-deleted documents were showing as raw IDs in responses instead of
being omitted.

## Key Changes

In the dataloader, trash-enabled collections now fetch with `trash:
true` so soft-deleted documents are returned alongside live ones.
`deletedAt` is merged into the select to ensure it's always present in
the result.

In `populate()`, the returned doc is checked for `deletedAt`. If set,
the doc is trashed and `relationshipValue` is set to null. For hasMany,
null entries are filtered from the array after all row promises settle.
For single relationships, the field is set to null.

This correctly distinguishes trashed documents from inaccessible ones —
access-denied or permanently deleted documents still fall back to the
raw ID, unchanged from existing behavior. `depth: 0` is also unaffected.


Fixes #16022

---
- To see the specific tasks where the Asana app for GitHub is being
used, see below:
  - https://app.asana.com/0/0/1213860470196517