[inductor] Test for shape padding (#100493)
Summary:
This wasn't tested anywhere as far as I can tell, so it was breaking
on Triton updates that fiddled with the signature of `do_bench`
Test Plan: `test_shape_padding`
Differential Revision: D45499978
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100493
Approved by: https://github.com/Chillee, https://github.com/jansel
