Refactor ErrorIfUnsupportedForeignConstraintExists

We can define a function that takes 4 parameters like:
`referencingDistMethod, referencingReplicationModel, referencedDistMethod, referencedReplicationModel`

and then returns an enum to determine the referencing & referenced tables like `FKEY_REF_TO_DIST, FKEY_CITUS_LOCAL_TO_REF` etc.

And we can define several functions to error out for unsupported foreign keys like:
`ErrorOutForFKeyFromRefToDist`,
`ErrorOutForFKeyFromLocalToCitusLocal`

and use those functions both in `ErrorIfUnsupportedForeignConstraintExists` and across the codebase.

Then we can even move `ErrorIfUnsupportedForeignConstraintExists` function to pre process to simplify the way we process `AlterTable` commands