Add missing #include <cstdint> (#2540)

This is needed to define `uint64_t` later on.

Authors:
  - https://github.com/jakirkham

Approvers:
  - Micka (https://github.com/lowener)

URL: #2540

cpp/include/raft/util/integer_utils.hpp

@@ -25,6 +25,7 @@
 
 #include <raft/core/detail/macros.hpp>
 
+#include <cstdint>
 #include <limits>
 #include <stdexcept>
 #include <type_traits>