[dynamo][higher order op] Bugfixes to pass graph.lint (#102448)
This PR ensures that the subgraphs use the newly created placeholder for the primary inputs and free variables. Earlier, this was not happening, and graph.lint() was failing. I need `graph.lint()` in the followup PRs where I run an `Interpreter` on the subgraph to preserve the metadata information to AOT Autograd.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102448
Approved by: https://github.com/zou3519
