[jit] add `inlined_graph` method to ScriptFunctions (#33508)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33508
Ever since we switched to not inlining by default, some users have
complained since they relied on inlining occuring to, e.g. process the
graph with some other tool. Add an inlined_graph for convenience in
those cases.
Test Plan: Imported from OSS
Differential Revision: D19977638
Pulled By: suo
fbshipit-source-id: fe1fa92ff888959203d5d1995930d488b5f9e24c
