This bit scanner iterates populated bits in a BitBoard from the trailing (least-significant) end.
Rename BitScanner → LeadingBitScanner.
Factor implementation of these two into a macro.
Clean up iterator returned by BitBoard::occupied_squares
Implement BitBoard::occupied_squares_trailing
This struct implements an Iterator that returns the positions of the 1 bits in the u64.
BitBoard takes this iterator and maps it into Squares in the pieces() method.
This is laying the groundwork for an iterator over the pieces in a Position. 👀
