split_with_sizes with more test codegen (#3389)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/3389

Life is fun when the code-gen is more challenging than writing the operator itself.

1. Test codegen update to include vector of Tensor as output: `Tensor(a)[]`.
2. `aten.split_with_sizes.default`
3. `aten.split.Tensor`
4. Improve `DimUtils` for better dimension reasoning.
ghstack-source-id: 224398848
exported-using-ghexport

Reviewed By: SS-JIA

Differential Revision: D56660525

fbshipit-source-id: c16fc665ad07bb697d376d57c292f36053b707ac