Make Query Engine tests work on Vitess with no foreign keys

[pimeys]

In addition to Tom's work (in https://github.com/prisma/prisma-engines/pull/1957), we should be making the Query Engine tests work with Vitess that doesn't allow foreign key constraints.

We're currently having a branch that injects the right things to the datamodel for the Query Engine tests to run, and we have four failing tests:

[error] Failed tests:
[error] 	writes.nestedMutations.NestedAtomicNumberOperationsSpec
[error] 	writes.relations.CompoundForeignKeysWithMixedRequiredness
[error] 	writes.nestedMutations.alreadyConverted.NestedDeleteMutationInsideUpdateSpec
[error] 	writes.nestedMutations.alreadyConverted.NestedDeleteMutationInsideUpsertSpec

The working branch has a docker-compose.yml preventing foreign keys, that can be used for debugging.