Add support for ptd in runner (#8957)

partner engineers are calling ET via LlamaModule: https://github.com/pytorch/executorch/blob/main/extension/android/src/main/java/org/pytorch/executorch/LlamaModule.java

This is a wrapper around the runner: https://www.internalfb.com/code/fbsource/[90d251fc01a84871b679406d6dc855eb5ded82fd]/fbcode/executorch/examples/models/llama/runner/runner.cpp?lines=47

Differential Revision: [D70596210](https://our.internmc.facebook.com/intern/diff/D70596210/)

ghstack-source-id: 269741205
Pull Request resolved: https://github.com/pytorch/executorch/pull/8953

Co-authored-by: lucylq <lfq@meta.com>