add decimals argument to round (#66195)

Summary:
Fixes pytorch/pytorch#65908

Added a new overload instead of updating the current signature. (Had issues with JIT and **maybe** it would have been FC breaking)

TODO:

* [x] Don't compute `std::pow(10, decimals)` for each element.
* [x] Update docs (https://docs-preview.pytorch.org/66195/generated/torch.round.html?highlight=round#torch.round)
* [x] Add tests
* ~~Should we try to make it composite?~~
* ~~Should we add specialized test with more values of `decimals` outside of OpInfo with larger range of values in input tensor?~~

cc mruberry rgommers

Pull Request resolved: pytorch/pytorch#66195

Reviewed By: anjali411

Differential Revision: D31821385

Pulled By: mruberry

fbshipit-source-id: 9a03fcb809440f0c83530108284e69c345e1850f

nestedtensor/csrc/UnaryOps.cpp

@@ -180,7 +180,7 @@ TORCH_LIBRARY_IMPL(aten, NestedTensor, m) {
   // UNARY_OP(mvlgamma);
   UNARY_OP(neg);
   UNARY_OP(reciprocal);
-  UNARY_OP(round);
+  // UNARY_OP(round);
   UNARY_OP(rsqrt);
   UNARY_OP(sigmoid);
   UNARY_OP_INPLACE_METHOD(sign)

test/utils.py

@@ -184,7 +184,7 @@ def get_unary_C_functions():
         "nonzero",
         "real",
         "reciprocal",
-        "round",
+#        "round",
         "rsqrt",
         "sigmoid",
         "sign",
@@ -234,7 +234,7 @@ def get_unary_functions():
         'reciprocal',
         # 'relu', # TODO: no relu_out in aten
         # 'renorm', # TODO: Requires extra kwargs
-        'round',
+        # 'round', # TODO: has decimals arg (and in general depending on an exact signature is not supported)
         'rsqrt',
         'sigmoid',
         'sign',