Consolidate to centipawns conversion

avoid doing this calculations in multiple places.

closes https://github.com/official-stockfish/Stockfish/pull/4686

No functional change

src/uci.h

@@ -76,6 +76,7 @@ private:
 
 void init(OptionsMap&);
 void loop(int argc, char* argv[]);
+int to_cp(Value v);
 std::string value(Value v);
 std::string square(Square s);
 std::string move(Move m, bool chess960);