parallelize sort (#142391)

- use __gnu_parallel::sort for gcc compilations
- add a parallelized version of std::sort and std::stable_sort for non gcc compilations

Using __gnu_parallel::sort:
provides ~3.7x speed up for length 50000 sorts with NUM_THREADS=16 and NUM_THREADS=4 on aarch64

The performance is measured using the following script:
```python
import torch
import torch.autograd.profiler as profiler

torch.manual_seed(0)

N = 50000
x = torch.randn(N, dtype=torch.float)

with profiler.profile(with_stack=True, profile_memory=False, record_shapes=True) as prof:
    for i in range(1000):
        _, _ = torch.sort(x)

print(prof.key_averages(group_by_input_shape=True).table(sort_by='self_cpu_time_total', row_limit=10))

```

Pull Request resolved: https://github.com/pytorch/pytorch/pull/142391
Approved by: https://github.com/malfet

cmake/Codegen.cmake

@@ -389,6 +389,12 @@ if(INTERN_BUILD_ATEN_OPS)
       else(MSVC)
         set(EXTRA_FLAGS "-DCPU_CAPABILITY=${CPU_CAPABILITY} -DCPU_CAPABILITY_${CPU_CAPABILITY}")
       endif(MSVC)
+
+      # Only parallelize the SortingKernel for now to avoid side effects
+      if(${NAME} STREQUAL "native/cpu/SortingKernel.cpp" AND NOT MSVC AND USE_OMP)
+        string(APPEND EXTRA_FLAGS " -D_GLIBCXX_PARALLEL")
+      endif()
+
       # Disable certain warnings for GCC-9.X
       if(CMAKE_COMPILER_IS_GNUCXX)
         if(("${NAME}" STREQUAL "native/cpu/GridSamplerKernel.cpp") AND ("${CPU_CAPABILITY}" STREQUAL "DEFAULT"))