Fix compilation errors on latest clang 16.

[Changochen]

When testing with clang 16, the compilation fails:

In file included from /usr/local/google/home/yongheng/PolyGlot/srcs/internal/srcs/utils.cpp:21:
/usr/local/google/home/yongheng/PolyGlot/srcs/internal/include/utils.h:58:1: error: ‘uint64_t’ does not name a type
   58 | uint64_t ducking_hash(const void *key, int len);
      | ^~~~~~~~
/usr/local/google/home/yongheng/PolyGlot/srcs/internal/include/utils.h:35:1: note: ‘uint64_t’ is defined in header ‘<cstdint>’; did you forget to ‘#include <cstdint>’?
   34 | #include <vector>
  +++ |+#include <cstdint>