fix(db-mongodb): querying relationships with where clause as an object with several conditions (#11953)

Fixes https://github.com/payloadcms/payload/issues/11927

When trying to use the following notation:
```ts
const { docs } = await payload.find({
  collection: 'movies',
  depth: 0,
  where: {
    'director.name': { equals: 'Director1' },
    'director.localized': { equals: 'Director1_Localized' },
  },
})
```
Currently, it respects only the latest condition and the first is
ignored.

However, this works fine:
```ts
const { docs } = await payload.find({
  collection: 'movies',
  depth: 0,
  where: {
    and: [
      {
        'director.name': { equals: 'Director1' },
      },
      {
        'director.localized': { equals: 'Director1_Localized' },
      },
    ],
  },
})
```

But this should be an equivalent to
```
 where: {
    'director.name': { equals: 'Director1' },
    'director.localized': { equals: 'Director1_Localized' },
  },
```

packages/db-mongodb/src/queries/parseParams.ts

@@ -81,7 +81,19 @@ export async function parseParams({
                   [searchParam.path]: searchParam.value,
                 })
               } else {
-                result[searchParam.path] = searchParam.value
+                if (result[searchParam.path]) {
+                  if (!result.$and) {
+                    result.$and = []
+                  }
+
+                  result.$and.push({ [searchParam.path]: result[searchParam.path] })
+                  result.$and.push({
+                    [searchParam.path]: searchParam.value,
+                  })
+                  delete result[searchParam.path]
+                } else {
+                  result[searchParam.path] = searchParam.value
+                }
               }
             } else if (typeof searchParam?.value === 'object') {
               result = deepMergeWithCombinedArrays(result, searchParam.value ?? {}, {

test/relationships/int.spec.ts

@@ -336,6 +336,41 @@ describe('Relationships', () => {
         expect(query.docs).toHaveLength(1) // Due to limit: 1
       })
 
+      it('should allow querying by relationships with an object where as AND', async () => {
+        const director = await payload.create({
+          collection: 'directors',
+          data: { name: 'Director1', localized: 'Director1_Localized' },
+        })
+
+        const movie = await payload.create({
+          collection: 'movies',
+          data: { director: director.id },
+          depth: 0,
+        })
+
+        const { docs: trueRes } = await payload.find({
+          collection: 'movies',
+          depth: 0,
+          where: {
+            'director.name': { equals: 'Director1' },
+            'director.localized': { equals: 'Director1_Localized' },
+          },
+        })
+
+        expect(trueRes).toStrictEqual([movie])
+
+        const { docs: falseRes } = await payload.find({
+          collection: 'movies',
+          depth: 0,
+          where: {
+            'director.name': { equals: 'Director1_Fake' },
+            'director.localized': { equals: 'Director1_Localized' },
+          },
+        })
+
+        expect(falseRes).toStrictEqual([])
+      })
+
       it('should allow querying within blocks', async () => {
         const rel = await payload.create({
           collection: relationSlug,