Split CrateImplDefs in inherent and trait impls

This makes the intention of inherent vs. trait impls somewhat more
clear and also fixes (?) an issue where trait impls with an unresolved
trait were added as inherent impls instead (hence the test changes).

crates/ra_ide/src/goto_implementation.rs

@@ -219,6 +219,10 @@ impl T for &Foo {}
   #[derive(Copy)]
 //^^^^^^^^^^^^^^^
 struct Foo<|>;
+
+mod marker {
+    trait Copy {}
+}
 "#,
         );
     }