[Fusion] Ignore inapplicable type refinements on abstract types

[Coelho04]

Reported here #6727 (comment)

An interface can be distributed across multiple source schemas, and each schema may implement that interface with different concrete types. The planner currently fails when you specify a type refinement for a concrete type that doesn't exist in the source schema that provides the field returning the distributed interface.
Since a source schema can only return the concrete types it actually defines, we can safely ignore inapplicable type refinements during planning.

[CLAassistant]

All committers have signed the CLA.

[tobias-tengler]

Looks good! Thank you for your contribution :)
I took the liberty to clean up a bit and fix the Interface_Field_With_Only_Type_Refinements_Exclusive_To_Other_Schema test.

Once you sign the CLA, I can get this merged.