Allow for case-insensitive type matching in remote joins

Unfortunately, GraphQL schemas generated by different GraphQL servers use different cases for the same type. It is possible that one endpoint exposes `BigInt` as `BigInt` while another endpoint may name it `bigint`. Even though both columns reference the same data type and values, the remote join will fail with the error message:
`in table "foo": in remote relationship "bar": expected type "BigInt" but got "bigint"`.

While the spec mentions case-sensitive variable and type names, it may be in favour of the users to allow for case-insensitive type matching on remote joins.

Relevant issue: #6313

Start with the remote-join validation discussed in this issue and review related issue #6313. Identify the relevant implementation and test locations, then verify the expected behavior against the BigInt/bigint example; done when the requested matching behavior is covered.

Written by the indexing model from the issue text.