[board] Implement a test_position macro that prints a Position after it builds it

Update the sight tests to use test_position!
Remove a stray leftover mut.
Clean up the test imports.

board/src/macros.rs

@@ -18,3 +18,17 @@ macro_rules! position {
             .build()
     };
 }
+
+#[cfg(test)]
+#[macro_export]
+macro_rules! test_position {
+    [$($color:ident $shape:ident on $square:ident),* $(,)?] => {
+        {
+            let pos = $crate::PositionBuilder::new()
+                $(.place_piece(piece!($color $shape on $square)))*
+                .build();
+            println!("{pos}");
+            pos
+        }
+    };
+}