Simplify picking of evasion moves

Sort evasions before we start returning them in next_move() (just like
every other kind of move) instead of looking for the biggest element on
every call to next_move(). The bench number changes because the old
method is not equivalent to a stable sort.

Passed STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 132064 W: 34318 L: 34204 D: 63542
Ptnml(0-2): 392, 15522, 34106, 15604, 408
https://tests.stockfishchess.org/tests/view/6743fee086d5ee47d953f9ca

Passed LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 97542 W: 24899 L: 24757 D: 47886
Ptnml(0-2): 63, 10646, 27193, 10824, 45
https://tests.stockfishchess.org/tests/view/674509cd86d5ee47d953fb96

closes https://github.com/official-stockfish/Stockfish/pull/5700

Bench: 1094825

src/movepick.h

@@ -35,11 +35,6 @@ class Position;
 // a cut-off first.
 class MovePicker {
 
-    enum PickType {
-        Next,
-        Best
-    };
-
    public:
     MovePicker(const MovePicker&)            = delete;
     MovePicker& operator=(const MovePicker&) = delete;
@@ -57,7 +52,7 @@ class MovePicker {
     void skip_quiet_moves();
 
    private:
-    template<PickType T, typename Pred>
+    template<typename Pred>
     Move select(Pred);
     template<GenType>
     void     score();