feat: support any depth for relationships in findDistinct (#14090)

Follow up to https://github.com/payloadcms/payload/pull/14026

```ts
// Supported before
const relationResult = await payload.findDistinct({ collection: 'posts', field: 'relation1.title' })
// Supported now
const relationResult = await payload.findDistinct({ collection: 'posts', field: 'relation1.relation2.title' })
const relationResult = await payload.findDistinct({ collection: 'posts', field: 'relation1.relation2.relation3.title' })
```

test/database/getConfig.ts

@@ -54,6 +54,11 @@ export const getConfig: () => Partial<Config> = () => ({
           type: 'text',
           name: 'title',
         },
+        {
+          name: 'simple',
+          type: 'relationship',
+          relationTo: 'simple',
+        },
         {
           type: 'tabs',
           tabs: [
@@ -131,6 +136,11 @@ export const getConfig: () => Partial<Config> = () => ({
           name: 'categoryTitle',
           virtual: 'category.title',
         },
+        {
+          type: 'text',
+          name: 'categorySimpleText',
+          virtual: 'category.simple.text',
+        },
         {
           type: 'relationship',
           relationTo: 'categories',