Fix `tests/indexed-types/`

See https://github.com/IaFP/ghc/tree/wip/party-ctrs-ghc-9/testsuite/tests/indexed-types

These tests involve all four flavors of type families (data fams, open type fams, closed type fams, associated type fams). It's not imperative that they are all fixed, but we should comb through broken test cases to probe for flaws in our TF implementation.