Don't store DeclarationUses

Summary: `XRefsViaName` is similar to `DeclarationUses` but instead of storing the declaration, it stores the name. So, to find the predicate we only need to map de `Declaration` to the `Name` and then query `XRefsViaName`. This allows us to compute the predicate efficiently on the fly

Reviewed By: iamirzhan

Differential Revision: D75604029

fbshipit-source-id: e06ac9a962a586957b1bc329d17dd634a6ab695e

Author: rubmary

glean/schema/source/python.angle

@@ -207,9 +207,9 @@ predicate DeclarationUses:
     file: src.File,
     span: src.ByteSpan,
   }
-  stored {Decl, File, Span} where
+  {Decl, File, Span} where
+  DeclarationToName Decl -> Name;
   XRefsViaName { Name, File, Span };
-  DeclarationWithName {Name, Decl};
 
 predicate DirectXRefsByFile:
   {