Structured kernels/index add

[krshrimali]

This PR:

• Added out= variant
• Port to structured kernel
• Revise derivatives.yaml file
• Fix failures for complex support with autograd
• Revise tests (refactor OpInfo, if needed)

cc: @ysiraichi

[krshrimali]

======================================================================
ERROR: test_variant_consistency_eager_index_add_cpu_float32 (__main__.TestCommonCPU)
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Traceback (most recent call last):
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_device_type.py", line 373, in instantiated_test
    raise rte
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_device_type.py", line 368, in instantiated_test
    result = test(self, **param_kwargs)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_device_type.py", line 734, in test_wrapper
    return test(*args, **kwargs)
  File "/home/krshrimali/Documents/Quansight/pytorch/test/test_ops.py", line 468, in test_variant_consistency_eager
    _test_consistency_helper(samples, variants)
  File "/home/krshrimali/Documents/Quansight/pytorch/test/test_ops.py", line 433, in _test_consistency_helper
    output_process_fn_grad(expected_forward).sum().backward()
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/_tensor.py", line 320, in backward
    torch.autograd.backward(self, gradient, retain_graph, create_graph, inputs=inputs)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/__init__.py", line 154, in backward
    Variable._execution_engine.run_backward(
RuntimeError: derivative for aten::index_add is not implemented

======================================================================
ERROR: test_fn_grad_index_add_cpu_complex128 (__main__.TestGradientsCPU)
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Traceback (most recent call last):
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_device_type.py", line 373, in instantiated_test
    raise rte
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_device_type.py", line 368, in instantiated_test
    result = test(self, **param_kwargs)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_device_type.py", line 734, in test_wrapper
    return test(*args, **kwargs)
  File "/home/krshrimali/Documents/Quansight/pytorch/test/test_ops.py", line 594, in test_fn_grad
    self._grad_test_helper(device, dtype, op, op.get_op())
  File "/home/krshrimali/Documents/Quansight/pytorch/test/test_ops.py", line 579, in _grad_test_helper
    return self._check_helper(device, dtype, op, variant, 'gradcheck', check_forward_ad=check_forward_ad)
  File "/home/krshrimali/Documents/Quansight/pytorch/test/test_ops.py", line 555, in _check_helper
    self.assertTrue(gradcheck(fn, gradcheck_args,
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_utils.py", line 2686, in gradcheck
    return torch.autograd.gradcheck(fn, inputs, **kwargs)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/gradcheck.py", line 1263, in gradcheck
    return _gradcheck_helper(**args)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/gradcheck.py", line 1276, in _gradcheck_helper
    _gradcheck_real_imag(gradcheck_fn, func, func_out, tupled_inputs, outputs, eps,
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/gradcheck.py", line 937, in _gradcheck_real_imag
    gradcheck_fn(imag_fn, imag_func_out, tupled_inputs, imag_outputs, eps,
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/gradcheck.py", line 1165, in _fast_gradcheck
    analytical_vJu = _get_analytical_vJu_backward_mode(inputs, outputs, nondet_tol, check_grad_dtypes, all_v, all_u_dense)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/gradcheck.py", line 555, in _get_analytical_vJu_backward_mode
    all_vJ = _check_analytical_jacobian_attributes(inputs, output, nondet_tol, check_grad_dtypes,
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/gradcheck.py", line 528, in _check_analytical_jacobian_attributes
    vjps1 = _get_analytical_vjps_wrt_specific_output(vjp_fn, output.clone(), v)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/gradcheck.py", line 633, in _get_analytical_vjps_wrt_specific_output
    grad_inputs = vjp_fn(v.reshape(sample_output.shape))
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/gradcheck.py", line 524, in vjp_fn
    return torch.autograd.grad(output, diff_input_list, grad_output,
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/autograd/__init__.py", line 234, in grad
    return Variable._execution_engine.run_backward(
RuntimeError: derivative for aten::index_add is not implemented

======================================================================
FAIL: test_out_index_add_cpu_float32 (__main__.TestCommonCPU)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_device_type.py", line 368, in instantiated_test
    result = test(self, **param_kwargs)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_device_type.py", line 734, in test_wrapper
    return test(*args, **kwargs)
  File "/home/krshrimali/Documents/Quansight/pytorch/test/test_ops.py", line 253, in test_out
    self.assertEqual(expected, out)
  File "/home/krshrimali/Documents/Quansight/pytorch/torch/testing/_internal/common_utils.py", line 1875, in assertEqual
    super().assertTrue(result, msg=self._get_assert_msg(msg, debug_msg=debug_msg))
AssertionError: False is not true : Tensors failed to compare as equal!With rtol=1.3e-06 and atol=1e-05, found 25 element(s) (out of 25) whose difference(s) exceeded the margin of error (including 25 nan comparisons). The greatest difference was nan (3.817853033490371e+35 vs. nan), which occurred at index (0, 0).

[krshrimali]

All tests pass...! 🎉