Revert evaluation cache

And return on using TT as backing store for position
evaluations.

Tests (even on single thread) show eval cache was a regression.
In multi thread result should be even worst because eval cache
is a per-thread struct, while TT is shared.

After 4957 games at 15"+0.05 (single thread)
eval cache vs master 969 - 1093 - 2895  -9 ELO

So previous reported result of +18 ELO was probably due to an
issue in the testing framework (a bug in cutechess-cli) that
has been fixed in the meanwhile.

bench: 5386711

src/thread.h

@@ -22,7 +22,6 @@
 
 #include <vector>
 
-#include "evaluate.h"
 #include "material.h"
 #include "movepick.h"
 #include "pawns.h"
@@ -109,7 +108,6 @@ public:
   void wait_for_stop_or_ponderhit();
 
   SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
-  Eval::Table evalTable;
   Material::Table materialTable;
   Endgames endgames;
   Pawns::Table pawnsTable;