introduce model-level end2end tests to dim order tests with different delegate (#6093)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/6093

This diff introduced end2end tests on several models + delegation combinations.

Models: llama2, resnet18, mobilenet_v3
Delegate: no delegate, xnnpack

Reviewed By: digantdesai, larryliu0820

Differential Revision: D64174329

fbshipit-source-id: 0807e0282d136bf1ef6d5be88e0c9f8512580f38