Removing grid lowering

[apbose]

This PR addresses the issue #2665

1. Removing grid_sampler_2d from lowering ops
2. Adding grid_sampler.default and grid_sampler_2d.default to the CONVERTER key registry
3. Adding tests for grid_sampler.default and grid_sampler_2d.default tests
4. Restructing the test
5. Correcting the interpolation mode and padding mode in the tests

[apbose]

PR #2682 seems to adddress partially the above.

[gs-olive]

Would this need to be grid_sampler_aten_ops[op_name](x, grid)?

[apbose]

@gs-olive yes it could be but then in that case it would be something like-

   def test_grid(self, _, op_name, input_shape, dim_shape, padding_mode, interpolation_mode, align_corners):
        class TestModule(nn.Module):
            def __init__(self):
                super().__init__()

            def forward(self, x):
                grid = torch.randint(-1, 1, dim_shape, dtype=torch.float32)
                return grid_sampler_aten_ops[op_name](x, grid, padding_mode, interpolation_mode, align_corners)

        inputs = [torch.randn(input_shape, dtype=torch.float32)]
        grid_model = TestModule()
        self.run_test(grid_model, inputs)

It would be code design choice to either encapsulate it in the lambda function in the parameters, or declare it in the above way. In my opinion both should be good.

You could let me know if you think otherwise.

[gs-olive]

I see - this makes sense, thanks. In that case, it seems good to go - should just need a rebase to enable testing.