Improve torch::jit::as_{module,object} performance (#84399)
This caches the import of `torch.jit.ScriptModule`,
`torch.ScriptObject` and `torch.jit.RecursiveScriptClass`. I measure
a ~0.8 us performance uplift locally when calling a `torch.ops`
function with a `ScriptObject` argument.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/84399
Approved by: https://github.com/ezyang
