[Feature] Endgame Syzygy tablebases

[KYLChiu]

Requirements:

• Add SyzygyTablebase class (https://en.wikipedia.org/wiki/Endgame_tablebase), which essentially are databases solving all positions given there are only a certain number of pieces left. Please wrap the python-chess API here: https://python-chess.readthedocs.io/en/latest/syzygy.html. The structure should be fairly similar the OpeningBook class, see opening_book.py.
• Integrate it into engine.py, similar to what is done with OpeningBook.
• Please add tests.

You can download databases for testing on: https://syzygy-tables.info/?fen=4k3/8/8/8/8/8/8/4K3_w_-_-_0_1