fix: `findDistinct` by explicit ID paths in relationships and virtual fields (#14215)

Fixes `findDistinct` operation when the `field` argument is:
* an eplicit ID path inside a relationship like:
```ts
const distinct = await payload.findDistinct({ collection: 'posts', field: 'category.id' })
```
* A virtual field linked to a relationship ID field
```ts
[
  {
    type: 'relationship',
    relationTo: 'categories',
    name: 'category',
  },
  {
    type: 'number',
    name: 'categoryID',
    virtual: 'category.id',
  },
]

const distinct = await payload.findDistinct({ collection: 'posts', field: 'categoryID' })
```