Updating all call-sites of the legacy dispatcher registration API in fbcode to the new API. (#48178)

Summary:
Pull Request resolved: pytorch/pytorch#48178

I migrated all call sites that used the legacy dispatcher registration API (RegisterOperators()) to use the new API (TORCH_LIBRARY...). I found all call-sites by running `fbgs RegisterOperators()`. This includes several places, including other OSS code (nestedtensor, torchtext, torchvision). A few things to call out:

For simple ops that only had one registered kernel without a dispatch key, I replaced them with:
```
TORCH_LIBRARY_FRAGMENT(ns, m) {
   m.def("opName", fn_name);
}
```

For ops that registered to a specific dispatch key / had multiple kernels registered, I registered the common kernel (math/cpu) directly inside a `TORCH_LIBRARY_FRAGMENT` block, and registered any additional kernels from other files (e.g. cuda) in a separate `TORCH_LIBRARY_IMPL` block.

```
// cpu file
TORCH_LIBRARY_FRAGMENT(ns, m) {
  m.def("opName(schema_inputs) -> schema_outputs");
  m.impl("opName", torch::dispatch(c10::DispatchKey::CPU, TORCH_FN(cpu_kernel)));
}

// cuda file
TORCH_LIBRARY_IMPL(ns, CUDA, m) {
  m.impl("opName", torch::dispatch(c10::DispatchKey::CUDA, TORCH_FN(cuda_kernel)));
}
```
Special cases:

I found a few ops that used a (legacy) `CPUTensorId`/`CUDATensorId` dispatch key. Updated those to use CPU/CUDA- this seems safe because the keys are aliased to one another in `DispatchKey.h`

There were a handful of ops that registered a functor (function class) to the legacy API. As far as I could tell we don't allow this case in the new API, mainly because you can accomplish the same thing more cleanly with lambdas. Rather than delete the class I wrote a wrapper function on top of the class, which I passed to the new API.

There were a handful of ops that were registered only to a CUDA dispatch key. I put them inside a TORCH_LIBRARY_FRAGMENT block, and used a `def()` and `impl()` call like in case two above.

Test Plan: Imported from OSS

Reviewed By: ezyang

Differential Revision: D25056090

Pulled By: bdhirsh

fbshipit-source-id: 8f868b45f545e5da2f21924046e786850eba70d9

Author: bdhirsh

torchvision/csrc/cpu/video_reader/VideoReader.cpp

@@ -669,12 +669,9 @@ torch::List<torch::Tensor> probeVideoFromFile(std::string videoPath) {
 
 } // namespace video_reader
 
-static auto registry = torch::RegisterOperators()
-                           .op("video_reader::read_video_from_memory",
-                               &video_reader::readVideoFromMemory)
-                           .op("video_reader::read_video_from_file",
-                               &video_reader::readVideoFromFile)
-                           .op("video_reader::probe_video_from_memory",
-                               &video_reader::probeVideoFromMemory)
-                           .op("video_reader::probe_video_from_file",
-                               &video_reader::probeVideoFromFile);
+TORCH_LIBRARY_FRAGMENT(video_reader, m) {
+    m.def("read_video_from_memory", video_reader::readVideoFromMemory);
+    m.def("read_video_from_file", video_reader::readVideoFromFile);
+    m.def("probe_video_from_memory", video_reader::probeVideoFromMemory);
+    m.def("probe_video_from_file", video_reader::probeVideoFromFile);
+}

torchvision/csrc/vision.cpp

@@ -39,14 +39,14 @@ int64_t _cuda_version() {
 #endif
 }
 
-static auto registry =
-    torch::RegisterOperators()
-        .op("torchvision::nms", &nms)
-        .op("torchvision::roi_align(Tensor input, Tensor rois, float spatial_scale, int pooled_height, int pooled_width, int sampling_ratio, bool aligned) -> Tensor",
-            &roi_align)
-        .op("torchvision::roi_pool", &roi_pool)
-        .op("torchvision::_new_empty_tensor_op", &new_empty_tensor)
-        .op("torchvision::ps_roi_align", &ps_roi_align)
-        .op("torchvision::ps_roi_pool", &ps_roi_pool)
-        .op("torchvision::deform_conv2d", &deform_conv2d)
-        .op("torchvision::_cuda_version", &_cuda_version);
+TORCH_LIBRARY_FRAGMENT(torchvision, m) {
+    m.def("nms", nms);
+    m.def("roi_align(Tensor input, Tensor rois, float spatial_scale, int pooled_height, int pooled_width, int sampling_ratio, bool aligned) -> Tensor",
+        &roi_align);
+    m.def("roi_pool", roi_pool);
+    m.def("_new_empty_tensor_op", new_empty_tensor);
+    m.def("ps_roi_align", ps_roi_align);
+    m.def("ps_roi_pool", ps_roi_pool);
+    m.def("deform_conv2d", deform_conv2d);
+    m.def("_cuda_version", _cuda_version);
+}