[dynamo][guards] Avoid unnecessary stack copies. (#119115)
There is no need to make a `frame_summary_stack` copy in case it's not modified. Proposed change uses copy-on-write functional approach that is easy to understand and is more efficient in case `self.loc_in_frame` is `None`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119115
Approved by: https://github.com/Skylion007
