fix: querying by polymorphic join field relationTo with overrideAccess: false (#11999)

Previously, querying by polymorphic joins `relationTo` with
`overrideAccess: false` caused an error:
```
QueryError: The following paths cannot be queried: relationTo
```

As this field actually doesn't exist in the schema. Now, under condition
that the query comes from a polymorphic join we skip checking
`relationTo` field access.

test/joins/config.ts

@@ -222,6 +222,7 @@ export default buildConfigWithDefaults({
     },
     {
       slug: 'multiple-collections-parents',
+      access: { read: () => true },
       fields: [
         {
           type: 'join',
@@ -236,6 +237,7 @@ export default buildConfigWithDefaults({
     },
     {
       slug: 'multiple-collections-1',
+      access: { read: () => true },
       admin: { useAsTitle: 'title' },
       fields: [
         {
@@ -255,6 +257,7 @@ export default buildConfigWithDefaults({
     },
     {
       slug: 'multiple-collections-2',
+      access: { read: () => true },
       admin: { useAsTitle: 'title' },
       fields: [
         {