Qualcomm AI Engine Direct - add program validation (#4297)

Summary:
- update graph signature for get_fake_program to work properly
- make sure program is valid after capture_program
- retire cature_pre_autograd_graph
- fix release build error & make cross-compile flatcc deterministic
- some minor fix

Pull Request resolved: https://github.com/pytorch/executorch/pull/4297

Reviewed By: kirklandsign

Differential Revision: D59984308

Pulled By: cccclai

fbshipit-source-id: 9b2a3eaabbc175db6209b12af95639e96fe95b7b