Introduce separate butterfly history table for sorting root moves

Idea of this patch comes from the fact that current history heuristics
are mostly populated by low depth entries since our stat bonus reaches
maximum value at depth 5-6 and number of low depth nodes is much bigger
than number of high depth nodes. But it doesn't make a whole lost of
sense to use this low-depth centered histories to sort moves at root.
Current patch introduces special history table that is used exclusively
at root, it remembers which quiet moves were good and which quiet moves
were not good there and uses this information for move ordering.

Passed STC:
https://tests.stockfishchess.org/tests/view/66dda74adc53972b68218cc9
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 127680 W: 33579 L: 33126 D: 60975
Ptnml(0-2): 422, 15098, 32391, 15463, 466

Passed LTC:
https://tests.stockfishchess.org/tests/view/66dead2adc53972b68218d34
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 381978 W: 96958 L: 95923 D: 189097
Ptnml(0-2): 277, 42165, 105089, 43162, 296

closes https://github.com/official-stockfish/Stockfish/pull/5595

Bench: 1611283

src/movepick.h

@@ -171,9 +171,11 @@ class MovePicker {
                Move,
                Depth,
                const ButterflyHistory*,
+               const ButterflyHistory*,
                const CapturePieceToHistory*,
                const PieceToHistory**,
-               const PawnHistory*);
+               const PawnHistory*,
+               bool);
     MovePicker(const Position&, Move, int, const CapturePieceToHistory*);
     Move next_move(bool skipQuiets = false);
 
@@ -187,6 +189,7 @@ class MovePicker {
 
     const Position&              pos;
     const ButterflyHistory*      mainHistory;
+    const ButterflyHistory*      rootHistory;
     const CapturePieceToHistory* captureHistory;
     const PieceToHistory**       continuationHistory;
     const PawnHistory*           pawnHistory;
@@ -195,6 +198,7 @@ class MovePicker {
     int                          stage;
     int                          threshold;
     Depth                        depth;
+    bool                         rootNode;
     ExtMove                      moves[MAX_MOVES];
 };