benchmark

73871abc - Use dynamo's compile_times() API to get compilation time metrics

Use dynamo's compile_times() API to get compilation time metrics Summary: Running warmup iterations interacts poorly with correctness checking in cases where the model has some persistent state. But since we're doing this just to measure compilation time, we can instead simply ask dynamo how long it spent on compilation using `torch._dynamo.utils.compile_times`! This PR mostly backs out D44851940 "Add compilation time support" in favor of the `compile_times` approach. Reviewed By: xuzhao9 Differential Revision: D45395617 fbshipit-source-id: 0290ef19a01bf2ac0f0d92c0f4bad7083b57a0d9