trunk/22669c3e651acf2c35aa1f629a0e261a9617c902: [dynamo] Support math.sumprod with non-constant arguments (#198685)

发生了什么

Part of #195901 . This is the sumprod row I picked up in #195901 (comment) . Opening as a draft: the change and the text below were drafted with AI assistance (Claude) and the tests were run locally, and I still need to finish reviewing it before marking it ready. math.sumprod is registered as an in-graph function, so constant arguments are folded, but anything else (Fractions built in the frame, generators, user it…

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