Fix sum OpInfo for sparse sample inputs and assert coverage for sparse-enabled operators (#100391)
This PR enables sum tests for sparse sample inputs. Previously, the tests existed but were never run because the sum OpInfo instance was created without specifying `supports_sparse_*=True`. To avoid such mistakes in the future, the following PR https://github.com/pytorch/pytorch/pull/100392 enables the `supports_sparse_*` flags automatically when OpInfo creation specifies `sample_inputs_sparse_*_func`.
In addition, the PR applies several fixes to sum tests for sparse sample inputs.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100391
Approved by: https://github.com/cpuhrsch
