Interfaces should not work with input types

[ZeroIntensity]

based on this stackoverflow question, graphql doesn't support interfaces with input types, and yet strawberry allows this:

import strawberry

@strawberry.interface
class SomeInterface:
    some_arg: str

@strawberry.input
class SomeInput(SomeInterface): # this should throw an error
    another_arg: str

[scratchmex]

I think this could be implemented when #489 is done

[BryceBeagle]

Changes might be similar to #1222, but for input types instead of arguments