GH-35273: [C++] Add integer round kernels (#36289)

### Rationale for this change

Currently `round` casts integers to floats which causes undesired behavior.

### What changes are included in this PR?

Add round kernels for integer types.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.

* Closes: #35273

Lead-authored-by: Jin Shang <shangjin1997@gmail.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Co-authored-by: Weston Pace <weston.pace@gmail.com>
Signed-off-by: Antoine Pitrou <antoine@python.org>

Author: 3 people

cpp/src/arrow/compute/kernels/codegen_internal.h

@@ -199,6 +199,11 @@ template <typename T>
 using is_signed_integer_value =
     std::integral_constant<bool, std::is_integral<T>::value && std::is_signed<T>::value>;
 
+template <typename T>
+using is_integer_value =
+    std::integral_constant<bool, is_signed_integer_value<T>::value ||
+                                     is_unsigned_integer_value<T>::value>;
+
 template <typename T, typename R = T>
 using enable_if_signed_integer_value = enable_if_t<is_signed_integer_value<T>::value, R>;