Implement dbg_extremes_of

An alternative to #5431, implements one function `dbg_extremes_of` to keep track
of min and max.

closes https://github.com/official-stockfish/Stockfish/pull/5434

No functional change

src/misc.h

@@ -67,6 +67,8 @@ std::optional<std::string> read_file_to_string(const std::string& path);
 void dbg_hit_on(bool cond, int slot = 0);
 void dbg_mean_of(int64_t value, int slot = 0);
 void dbg_stdev_of(int64_t value, int slot = 0);
+void dbg_extremes_of(int64_t value, int slot);
+
 void dbg_correl_of(int64_t value1, int64_t value2, int slot = 0);
 void dbg_print();