Remove uncessary unalias_nested calls when creating a logical plan

[alamb]

          My thought is to execute `unalias_nested` when creating the initial logical plan. 

But the current implementation is also acceptable to me. Thank you @samuelcolvin . If we follow the current implementation, we also need to remove the redundant unalias_nested calls outside of try_new.

cc @alamb

Originally posted by @jonahgao in #11307 (comment)