Rust: fix <X as Y> path extraction

This works around a quirk in rust-analyzer's AST generation machinery,
where for an `<X as Y>` path there might be no way to directly get `Y`
from the path segment.

rust/schema/annotations.py

@@ -1439,7 +1439,8 @@ class _:
     """
     A path segment, which is one part of a whole path.
     """
-
+    type_repr: optional["TypeRepr"] | child | rust.detach
+    trait_type_repr: optional["PathTypeRepr"] | child | rust.detach
 
 @annotate(PathTypeRepr)
 @qltest.test_with(Path)