Auto merge of #14513 - hecatia-elegua:alias-based-completion2, r=Veykril

doc(alias)-based completion round 2

Follow-up on #14433
We can now complete fields, functions and some use/mods.
Flyimports don't behave, I don't really have the time to understand the structure there either.
While reading the flyimport code, I removed one method only used there, the closure-tree was a bit confusing, I can revert that if you want.

crates/ide-completion/src/render/function.rs

@@ -147,6 +147,8 @@ fn render(
             }
         }
     }
+
+    item.doc_aliases(ctx.doc_aliases);
     item
 }