[board] Clean up a bunch of build errors

Fix imports to refer to core and bitboard crates.
Fix some API use errors.

board/src/position/builders/move_builder.rs

@@ -4,8 +4,9 @@ use crate::{
     piece::{PlacedPiece, Shape},
     position::flags::Flags,
     r#move::Castle,
-    BitBoard, Color, MakeMoveError, Move, Piece, Position,
+    Color, MakeMoveError, Move, Piece, Position,
 };
+use chessfriend_bitboard::BitBoard;
 use chessfriend_core::{Direction, Square};
 
 /// A position builder that builds a new position by making a move.