fix(drizzle)!: localized fields uniqueness per locale (#8230)

Previously, this worked with MongoDB but failed with Postgres / SQLite
when the `slug` field has both `localized: true` and `unique: true`.

```ts
await payload.create({
  collection: "posts",
  locale: "en",
  data: {
    slug: "my-post"
  }
})

await payload.create({
  collection: "posts",
  locale: "de",
  data: {
    slug: "my-post"
  }
})
```

Now, we build unique constraints and indexes in combination with the
_locale column. This should also improve query performance for fields
with both index: true and localized: true.

### Migration steps (Postgres/SQLite only)
This change updates the database schema and requires a migration (if you
have any localized fields). To apply it, run the following commands:

```sh
pnpm payload migration:create locale_unique_indexes
pnpm payload migrate
```

Note that if you use `db.push: true` which is a default, you don't have
to run `pnpm payload migrate` in the development mode, only in the
production, as Payload automatically pushes the schema to your DB with
it.

test/localization/int.spec.ts

@@ -1,6 +1,5 @@
-import type { Payload, Where } from 'payload'
-
 import path from 'path'
+import { type Payload, type Where } from 'payload'
 import { fileURLToPath } from 'url'
 
 import type { NextRESTClient } from '../helpers/NextRESTClient.js'
@@ -1954,6 +1953,44 @@ describe('Localization', () => {
       expect(retrieved.array.es[0].text).toEqual(['hola', 'adios'])
     })
   })
+
+  describe('localized with unique', () => {
+    it('localized with unique should work for each locale', async () => {
+      await payload.create({
+        collection: 'localized-posts',
+        locale: 'ar',
+        data: {
+          unique: 'text',
+        },
+      })
+
+      await payload.create({
+        collection: 'localized-posts',
+        locale: 'en',
+        data: {
+          unique: 'text',
+        },
+      })
+
+      await payload.create({
+        collection: 'localized-posts',
+        locale: 'es',
+        data: {
+          unique: 'text',
+        },
+      })
+
+      await expect(
+        payload.create({
+          collection: 'localized-posts',
+          locale: 'en',
+          data: {
+            unique: 'text',
+          },
+        }),
+      ).rejects.toBeTruthy()
+    })
+  })
 })
 
 async function createLocalizedPost(data: {