[export] manuually create test cases for split and inline (#119914)
This PR makes the tests for inline and sequential_split stop relying on set_grad_enabled to be in the graph. Because they'll be gone if we turn on the replace_set_grad_with_hop_pass in the following diff. Instead, we'll manually insert them into the graph.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119914
Approved by: https://github.com/tugsbayasgalan
ghstack dependencies: #119732, #119736, #119810, #119913
