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/fields/upload.mdx

@@ -49,6 +49,7 @@ caption="Admin panel screenshot of an Upload field"
 | **`access`**         | Provide field-based access control to denote what users can see and do with this field's data. [More](/docs/fields/overview#field-level-access-control)                     |
 | **`hidden`**         | Restrict this field's visibility from all APIs entirely. Will still be saved to the database, but will not appear in any API or the Admin panel.                            |
 | **`defaultValue`**   | Provide data to be used for this field's default value. [More](/docs/fields/overview#default-values)                                                                        |
+| **`displayPreview`** | Enable displaying preview of the uploaded file. Overrides related Collection's `displayPreview` option. [More](/docs/upload/overview#collection-upload-options).            |
 | **`localized`**      | Enable localization for this field. Requires [localization to be enabled](/docs/configuration/localization) in the Base config.                                             |
 | **`required`**       | Require this field to have a value.                                                                                                                                         |
 | **`admin`**          | Admin-specific configuration. See the [default field admin config](/docs/fields/overview#admin-config) for more details.                                                    |