caffe2/torch/csrc/jit/frontend/tree_views: workaround nvcc compiler error

Test Plan:
Move it outside the header so it's not seen by nvcc

```
$ buck2 build -c fbcode.platform=platform010 fbcode//accelerators/pytorch/lib/cuda:ngram_repeat_block_cuda
Downloading buck2...
[======================================================================]

watchman fresh instance event, clearing cache
Using disallowed linker flag 'arvr/third-party/toolchains/platform009/build/mesa/lib/libGL.so' in library rule 'fbsource//third-party/toolchains:opengl'
Using disallowed linker flag 'arvr/third-party/freeglut/3.0.0/libs/x64-linux/libglut.a' in library rule 'fbsource//third-party/toolchains:GLUT'
Action Failed for fbcode//accelerators/pytorch/lib/cuda:ngram_repeat_block_cuda (ovr_config//platform/linux:x86_64-fbcode-platform010-clang-6dbc4bb1b9a32829)#5:
cxx_compile ngram_repeat_block_cuda_kernel.cu (pic) failed with non-zero exit code 1
debug information: action_digest=b2bda91d24dad53e960c740ef9a412cee1902d86:94
stdout:
stderr:
fbcode/caffe2/torch/csrc/jit/frontend/tree_views.h: In instantiation of 'static torch::jit::Maybe<T> torch::jit::Maybe<T>::create(const torch::jit::SourceRange&, const T&) [with T = torch::jit::List<torch::jit::Property>]':
fbcode/caffe2/torch/csrc/jit/frontend/tree_views.h:505:117:   required from here
fbcode/caffe2/torch/csrc/jit/frontend/tree_views.h:220:33: error: cannot convert 'const torch::jit::List<torch::jit::Property>' to 'torch::jit::TreeList&&' {aka 'c10::SmallVector<c10::intrusive_ptr<torch::jit::Tree>, 4>&&'}
  220 |     return Maybe<T>(Compound::create(TK_OPTION, range, {value}));
      |                ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
fbcode/caffe2/torch/csrc/jit/frontend/tree.h:144:1: note:   initializing argument 3 of 'static torch::jit::TreeRef torch::jit::Compound::create(int, const torch::jit::SourceRange&, torch::jit::TreeList&&)'
  143 |       const SourceRange& range_,
      |         ~~~~~~~~~~~~~~~~~~~~~~~~
  144 |       TreeList&& trees_) {
      | ^
fbcode/caffe2/torch/csrc/jit/frontend/tree_views.h: In instantiation of 'static torch::jit::Maybe<T> torch::jit::Maybe<T>::create(const torch::jit::SourceRange&, const T&) [with T = torch::jit::List<torch::jit::Assign>]':
fbcode/caffe2/torch/csrc/jit/frontend/tree_views.h:505:171:   required from here
fbcode/caffe2/torch/csrc/jit/frontend/tree_views.h:220:33: error: cannot convert 'const torch::jit::List<torch::jit::Assign>' to 'torch::jit::TreeList&&' {aka 'c10::SmallVector<c10::intrusive_ptr<torch::jit::Tree>, 4>&&'}
  220 |     return Maybe<T>(Compound::create(TK_OPTION, range, {value}));
      |                ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
fbcode/caffe2/torch/csrc/jit/frontend/tree.h:144:1: note:   initializing argument 3 of 'static torch::jit::TreeRef torch::jit::Compound::create(int, const torch::jit::SourceRange&, torch::jit::TreeList&&)'
  143 |       const SourceRange& range_,
      |         ~~~~~~~~~~~~~~~~~~~~~~~~
  144 |       TreeList&& trees_) {
      | ^
cc1plus: note: unrecognized command-line option '-Wno-ignored-optimization-argument' may have been intended to silence earlier diagnostics
cc1plus: note: unrecognized command-line option '-Wno-ambiguous-reversed-operator' may have been intended to silence earlier diagnostics
cc1plus: note: unrecognized command-line option '-Wno-ignored-optimization-argument' may have been intended to silence earlier diagnostics
cc1plus: note: unrecognized command-line option '-Wno-ambiguous-reversed-operator' may have been intended to silence earlier diagnostics
command: buck-out/v2/gen/fbcode/999b02f9444004c1/tools/build/__wrap_nvcc.py__/wrap_nvcc.py -_NVCC_BIN_ fbcode ...<omitted>... ors/pytorch/lib/cuda/__ngram_repeat_block_cuda__/__objects__/ngram_repeat_block_cuda_kernel.cu.pic.o (rerun with -v to view the untruncated command)

```

Reviewed By: zhxchen17

Differential Revision: D33592885

fbshipit-source-id: a36dcb3c8265d009b2287f0a479695d1ddbf85aa

Author: luciang

torch/csrc/jit/frontend/tree_views.cpp

@@ -36,5 +36,22 @@ std::vector<std::string> getUnresolvedClassAttributes(const ClassDef& def) {
   return ret;
 }
 
+/* static */ ClassDef ClassDef::create(
+    const SourceRange& range,
+    const Ident& name,
+    const Maybe<Expr>& superclass,
+    const List<Stmt>& body,
+    const List<Property>& properties,
+    const List<Assign>& assigns) {
+  return ClassDef(Compound::create(
+      TK_CLASS_DEF,
+      range,
+      {name,
+       superclass,
+       body,
+       Maybe<List<Property>>::create(range, properties),
+       Maybe<List<Assign>>::create(range, assigns)}));
+}
+
 } // namespace jit
 } // namespace torch

torch/csrc/jit/frontend/tree_views.h

@@ -501,16 +501,7 @@ struct ClassDef : public TreeView {
       const Maybe<Expr>& superclass,
       const List<Stmt>& body,
       const List<Property>& properties,
-      const List<Assign>& assigns) {
-    return ClassDef(Compound::create(
-        TK_CLASS_DEF,
-        range,
-        {name,
-         superclass,
-         body,
-         Maybe<List<Property>>::create(range, properties),
-         Maybe<List<Assign>>::create(range, assigns)}));
-  }
+      const List<Assign>& assigns);
 };
 
 TORCH_API std::vector<std::string> getUnresolvedClassAttributes(