feat: add join field config where property (#8973)

### What?

Makes it possible to filter join documents using a `where` added
directly in the config.


### Why?

It makes the join field more powerful for adding contextual meaning to
the documents being returned. For example, maybe you have a
`requiresAction` field that you set and you can have a join that
automatically filters the documents to those that need attention.

### How?

In the database adapter, we merge the requested `where` to the `where`
defined on the field.
On the frontend the results are filtered using the `filterOptions`
property in the component.

Fixes
https://github.com/payloadcms/payload/discussions/8936
https://github.com/payloadcms/payload/discussions/8937

---------

Co-authored-by: Sasha <64744993+r1tsuu@users.noreply.github.com>

test/joins/collections/Categories.ts

@@ -90,5 +90,14 @@ export const Categories: CollectionConfig = {
       collection: singularSlug,
       on: 'category',
     },
+    {
+      name: 'filtered',
+      type: 'join',
+      collection: postsSlug,
+      on: 'category',
+      where: {
+        isFiltered: { not_equals: true },
+      },
+    },
   ],
 }