Refactor global variables

This aims to remove some of the annoying global structure which Stockfish has.

Overall there is no major elo regression to be expected.

Non regression SMP STC (paused, early version):
https://tests.stockfishchess.org/tests/view/65983d7979aa8af82b9608f1
LLR: 0.23 (-2.94,2.94) <-1.75,0.25>
Total: 76232 W: 19035 L: 19096 D: 38101
Ptnml(0-2): 92, 8735, 20515, 8690, 84

Non regression STC (early version):
https://tests.stockfishchess.org/tests/view/6595b3a479aa8af82b95da7f
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 185344 W: 47027 L: 46972 D: 91345
Ptnml(0-2): 571, 21285, 48943, 21264, 609

Non regression SMP STC:
https://tests.stockfishchess.org/tests/view/65a0715c79aa8af82b96b7e4
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 142936 W: 35761 L: 35662 D: 71513
Ptnml(0-2): 209, 16400, 38135, 16531, 193

These global structures/variables add hidden dependencies and allow data
to be mutable from where it shouldn't it be (i.e. options). They also
prevent Stockfish from internal selfplay, which would be a nice thing to
be able to do, i.e. instantiate two Stockfish instances and let them
play against each other. It will also allow us to make Stockfish a
library, which can be easier used on other platforms.

For consistency with the old search code, `thisThread` has been kept,
even though it is not strictly necessary anymore. This the first major
refactor of this kind (in recent time), and future changes are required,
to achieve the previously described goals. This includes cleaning up the
dependencies, transforming the network to be self contained and coming
up with a plan to deal with proper tablebase memory management (see
comments for more information on this).

The removal of these global structures has been discussed in parts with
Vondele and Sopel.

closes https://github.com/official-stockfish/Stockfish/pull/4968

No functional change

src/syzygy/tbprobe.cpp

@@ -42,7 +42,6 @@
 #include "../position.h"
 #include "../search.h"
 #include "../types.h"
-#include "../uci.h"
 
 #ifndef _WIN32
     #include <fcntl.h>
@@ -1574,7 +1573,7 @@ int Tablebases::probe_dtz(Position& pos, ProbeState* result) {
 // Use the DTZ tables to rank root moves.
 //
 // A return value false indicates that not all probes were successful.
-bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) {
+bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves, bool rule50) {
 
     ProbeState result = OK;
     StateInfo  st;
@@ -1585,7 +1584,7 @@ bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) {
     // Check whether a position was repeated since the last zeroing move.
     bool rep = pos.has_repeated();
 
-    int dtz, bound = Options["Syzygy50MoveRule"] ? (MAX_DTZ - 100) : 1;
+    int dtz, bound = rule50 ? (MAX_DTZ - 100) : 1;
 
     // Probe and rank each move
     for (auto& m : rootMoves)
@@ -1647,7 +1646,7 @@ bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) {
 // This is a fallback for the case that some or all DTZ tables are missing.
 //
 // A return value false indicates that not all probes were successful.
-bool Tablebases::root_probe_wdl(Position& pos, Search::RootMoves& rootMoves) {
+bool Tablebases::root_probe_wdl(Position& pos, Search::RootMoves& rootMoves, bool rule50) {
 
     static const int WDL_to_rank[] = {-MAX_DTZ, -MAX_DTZ + 101, 0, MAX_DTZ - 101, MAX_DTZ};
 
@@ -1655,7 +1654,6 @@ bool Tablebases::root_probe_wdl(Position& pos, Search::RootMoves& rootMoves) {
     StateInfo  st;
     WDLScore   wdl;
 
-    bool rule50 = Options["Syzygy50MoveRule"];
 
     // Probe and rank each move
     for (auto& m : rootMoves)

src/syzygy/tbprobe.h

@@ -25,6 +25,7 @@
 
 namespace Stockfish {
 class Position;
+class OptionsMap;
 }
 
 namespace Stockfish::Tablebases {
@@ -47,12 +48,13 @@ enum ProbeState {
 
 extern int MaxCardinality;
 
+
 void     init(const std::string& paths);
 WDLScore probe_wdl(Position& pos, ProbeState* result);
 int      probe_dtz(Position& pos, ProbeState* result);
-bool     root_probe(Position& pos, Search::RootMoves& rootMoves);
-bool     root_probe_wdl(Position& pos, Search::RootMoves& rootMoves);
-void     rank_root_moves(Position& pos, Search::RootMoves& rootMoves);
+bool     root_probe(Position& pos, Search::RootMoves& rootMoves, bool rule50);
+bool     root_probe_wdl(Position& pos, Search::RootMoves& rootMoves, bool rule50);
+void     rank_root_moves(const OptionsMap& options, Position& pos, Search::RootMoves& rootMoves);
 
 }  // namespace Stockfish::Tablebases