feat: adds upload's relationship thumbnail (#5015)

## Description

I've made an implementation of the feature requested here:
https://github.com/payloadcms/payload/discussions/3407

Before:
![CleanShot 2024-02-07 at 00 39
47](https://github.com/payloadcms/payload/assets/34719093/4b182118-41bd-47f7-af03-a0b739f7e407)

After:
![CleanShot 2024-02-07 at 00 40
17](https://github.com/payloadcms/payload/assets/34719093/d813de81-bab5-40b2-b31c-5a7ee107dabd)


- [x] I have read and understand the
[CONTRIBUTING.md](https://github.com/payloadcms/payload/blob/main/CONTRIBUTING.md)
document in this repository.

## Type of change

<!-- Please delete options that are not relevant. -->

- [x] New feature (non-breaking change which adds functionality)

## Checklist:

- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] Existing test suite passes locally with my changes

docs/upload/overview.mdx

@@ -47,6 +47,7 @@ Every Payload Collection can opt-in to supporting Uploads by specifying the `upl
 | **`adminThumbnail`**           | Set the way that the Admin panel will display thumbnails for this Collection. [More](#admin-thumbnails)                                                                                 |
 | **`crop`**                     | Set to `false` to disable the cropping tool in the Admin panel. Crop is enabled by default. [More](#crop-and-focal-point-selector)                                                      |
 | **`disableLocalStorage`**      | Completely disable uploading files to disk locally. [More](#disabling-local-upload-storage)                                                                                             |
+| **`displayPreview`**           | Enable displaying preview of the uploaded file in Upload fields related to this Collection. Can be locally overridden by `displayPreview` option in Upload field. [More](/docs/fields/upload#config). |
 | **`externalFileHeaderFilter`** | Accepts existing headers and can filter/modify them.                                                                                                                                    |
 | **`focalPoint`**               | Set to `false` to disable the focal point selection tool in the Admin panel. The focal point selector is only available when `imageSizes` or `resizeOptions` are defined. [More](#crop-and-focal-point-selector) |
 | **`formatOptions`**            | An object with `format` and `options` that are used with the Sharp image library to format the upload file. [More](https://sharp.pixelplumbing.com/api-output#toformat)                 |