Reduce size of eval to i16

src/search/transposition_table.rs

@@ -31,7 +31,7 @@ pub struct TTEntry {
     pub hash: ZobristHash,
     pub mv: Option<Move>,
     pub depth: u8,
-    pub score: i32,
+    pub score: i16,
     pub node_type: NodeType,
 }
 
@@ -40,7 +40,7 @@ impl TTEntry {
         hash: ZobristHash,
         mv: Option<Move>,
         depth: u8,
-        score: i32,
+        score: i16,
         node_type: NodeType,
     ) -> Self {
         Self {