Fix #10452: Don't let AyStar max_search_nodes unattended when initializing (#11544)

Add a constant with the default value of 10000 and have the pathfinding settings refer to it.

Add a preventative method to AyStar when it's initializing, to limit the number of max_search_nodes if left unattended.

src/pathfinder/npf/aystar.cpp

@@ -301,4 +301,7 @@ void AyStar::Init(Hash_HashProc hash, uint num_buckets)
 	 *  When that one gets full it reserves another one, till this number
 	 *  That is why it can stay this high */
 	this->openlist_queue.Init(102400);
+
+	/* Set a reasonable default limit */
+	this->max_search_nodes = AYSTAR_DEF_MAX_SEARCH_NODES;
 }

src/pathfinder/npf/aystar.h

@@ -20,6 +20,8 @@
 #include "../../tile_type.h"
 #include "../../track_type.h"
 
+static const int AYSTAR_DEF_MAX_SEARCH_NODES = 10000; ///< Reference limit for #AyStar::max_search_nodes
+
 /** Return status of #AyStar methods. */
 enum AystarStatus {
 	AYSTAR_FOUND_END_NODE, ///< An end node was found.

src/pathfinder/pathfinder_type.h

@@ -11,6 +11,7 @@
 #define PATHFINDER_TYPE_H
 
 #include "../tile_type.h"
+#include "npf/aystar.h"
 
 /** Length (penalty) of one tile with NPF */
 static const int NPF_TILE_LENGTH = 100;

src/table/settings/pathfinding_settings.ini

@@ -168,7 +168,7 @@ cat      = SC_EXPERT
 [SDT_VAR]
 var      = pf.npf.npf_max_search_nodes
 type     = SLE_UINT
-def      = 10000
+def      = AYSTAR_DEF_MAX_SEARCH_NODES
 min      = 500
 max      = 100000
 cat      = SC_EXPERT
@@ -325,7 +325,7 @@ cat      = SC_EXPERT
 var      = pf.yapf.max_search_nodes
 type     = SLE_UINT
 from     = SLV_28
-def      = 10000
+def      = AYSTAR_DEF_MAX_SEARCH_NODES
 min      = 500
 max      = 1000000
 cat      = SC_EXPERT