Add UI tests for crate renaming

[jsdw]

#145 adds the ability to tell scale-info where the crate lives, which is super handy in some circumstances.

let's add a couple of UI tests for this feature.

Potentially we can rename scale-info in the test Cargo.toml and then use foo::{self as scale_info}; at the top of most tests to expose it in the "usual place", and then we can fully test that #[scale_info(crate = "foo")] works when it is only present under eg foo::.