feat: add findDistinct operation (#13102)

Adds a new operation findDistinct that can give you distinct values of a
field for a given collection
Example:
Assume you have a collection posts with multiple documents, and some of
them share the same title:
```js
// Example dataset (some titles appear multiple times)
[
  { title: 'title-1' },
  { title: 'title-2' },
  { title: 'title-1' },
  { title: 'title-3' },
  { title: 'title-2' },
  { title: 'title-4' },
  { title: 'title-5' },
  { title: 'title-6' },
  { title: 'title-7' },
  { title: 'title-8' },
  { title: 'title-9' },
]
```
You can now retrieve all unique title values using findDistinct:
```js
const result = await payload.findDistinct({
  collection: 'posts',
  field: 'title',
})

console.log(result.values)
// Output:
// [
//   'title-1',
//   'title-2',
//   'title-3',
//   'title-4',
//   'title-5',
//   'title-6',
//   'title-7',
//   'title-8',
//   'title-9'
// ]
```
You can also limit the number of distinct results:
```js
const limitedResult = await payload.findDistinct({
  collection: 'posts',
  field: 'title',
  sortOrder: 'desc',
  limit: 3,
})

console.log(limitedResult.values)
// Output:
// [
//   'title-1',
//   'title-2',
//   'title-3'
// ]
```

You can also pass a `where` query to filter the documents.

docs/local-api/overview.mdx

@@ -194,6 +194,27 @@ const result = await payload.count({
 })
 ```
 
+### FindDistinct#collection-find-distinct
+
+```js
+// Result will be an object with:
+// {
+//   values: ['value-1', 'value-2'], // array of distinct values,
+//   field: 'title', // the field
+//   totalDocs: 10, // count of the distinct values satisfies query,
+//   perPage: 10, // count of distinct values per page (based on provided limit)
+// }
+const result = await payload.findDistinct({
+  collection: 'posts', // required
+  locale: 'en',
+  where: {}, // pass a `where` query here
+  user: dummyUser,
+  overrideAccess: false,
+  field: 'title',
+  sort: 'title',
+})
+```
+
 ### Update by ID#collection-update-by-id
 
 ```js