[Feature Request] Support field comparison in access policy rules

[ymc9]

Today policy rules allow you to do comparisons but only one field can be involved in an expression, which means with:

model Foo {
  x Int
  y Int
}

@@allow(x > 0) is valid, but @@allow(x > y) is rejected at compile time.

Prisma has a preview feature called fieldReference which allows you to compare between fields in the same table. We can use that to relax some of the restrictions here.