[board] Export BitBoard directly off of the crate for internal use

Update all the imports to import from the crate directly.

board/src/moves/queen.rs

@@ -2,10 +2,9 @@
 
 use super::{move_generator_declaration, MoveGeneratorInternal, MoveSet};
 use crate::{
-    bitboard::BitBoard,
     piece::{Color, Piece, PlacedPiece},
     square::Direction,
-    Move, Position,
+    BitBoard, Move, Position,
 };
 
 move_generator_declaration!(ClassicalMoveGenerator);
@@ -68,10 +67,9 @@ impl<'pos> MoveGeneratorInternal for ClassicalMoveGenerator<'pos> {
 mod tests {
     use super::*;
     use crate::{
-        bitboard::BitBoard,
         piece::{Color, Piece},
         position::DiagramFormatter,
-        Position, Square,
+        BitBoard, Position, Square,
     };
 
     #[test]