Disable view_copy elimination for graph outputs (#3565)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/3565

If the `view_copy` op is a graph output, leave it as a view_copy for now since the output pointer may be modified at runtime when deploying on device.

Right now, the modified pointer would be ignored since the view_copy op will always point to its predecessor memory.

cc chrismthompson jcoriell fengwang

Reviewed By: JacobSzwejbka, metascroy

Differential Revision: D57132664

fbshipit-source-id: b97bd81166b728c306fae8b212aeb5e38348b391