Migrate convolution workgroup API (#3996)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/3996

The expectation these days is to always use the `ComputeGraph` API; we've just been lazy with migration. Doing convolution now since I'm playing with the workgroup size.
ghstack-source-id: 230551344

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Reviewed By: nathanaelsee

Differential Revision: D58681683

fbshipit-source-id: e789018c59417c4e8c0649e89c87492a01be314a