Tests for castling move generation

[divy-07]

Add tests in src/test/java/chess/moves/CastlePossibleMoveTest.java

We need to account for:

• basic castling (only king and rook nothing special)
• castling both sides by both colors
• no castling when a piece is between king and rook
• no castling when king/rook has already moved
• no castling when king/rook not on home square
• no castling when king has to move through check

[divy-07]

Also need to add Knight move generation tests, no idea how that escaped my mind