[export] Make pass base composable (#103701)
Moving ExportTracer so that EXIR can subclass it to do handling for delegates, and ExportPassBase can use the correct tracer. Upstreaming OSS changes in D45884895 first
Pull Request resolved: https://github.com/pytorch/pytorch/pull/103701
Approved by: https://github.com/avikchaudhuri, https://github.com/tugsbayasgalan, https://github.com/ydwu4
