Remove Stack/thread dependence in movepick

as a lower level routine, movepicker should not depend on the
search stack or the thread class, removing a circular dependency.
Instead of copying the search stack into the movepicker object,
as well as accessing the thread class for one of the histories,
pass the required fields explicitly to the constructor (removing
the need for thread.h and implicitly search.h in movepick.cpp).
The signature is thus longer, but more explicit:

Also some renaming of histories structures while there.

passed STC [-3,1], suggesting a small elo impact:

LLR: 3.13 (-2.94,2.94) [-3.00,1.00]
Total: 381053 W: 68071 L: 68551 D: 244431
elo =   -0.438 +-    0.660 LOS:    9.7%

No functional change.

src/thread.h

@@ -67,9 +67,9 @@ public:
   Search::RootMoves rootMoves;
   Depth rootDepth;
   Depth completedDepth;
-  CounterMoveStat counterMoves;
-  ButterflyHistory history;
-  CounterMoveHistoryStat counterMoveHistory;
+  CounterMoveHistory counterMoves;
+  ButterflyHistory mainHistory;
+  ContinuationHistory contHistory;
 };