[board, core, moves, position] Implement castling

Implement a new method on Position that evaluates whether the active color can castle
on a given wing of the board. Then, implement making a castling move in the position.

Make a new Wing enum in the core crate to specify kingside or queenside. Replace the
Castle enum from the board crate with this one. This caused a lot of churn...

Along the way fix a bunch of tests.

Note: there's still no way to actually make a castling move in explorer.

core/src/coordinates.rs

@@ -1,5 +1,9 @@
 // Eryn Wells <eryn@erynwells.me>
 
+mod wings;
+
+pub use wings::Wing;
+
 use crate::Color;
 use std::fmt;
 use thiserror::Error;
@@ -519,7 +523,7 @@ mod tests {
     fn bad_algebraic_input() {
         assert!("a0".parse::<Square>().is_err());
         assert!("j3".parse::<Square>().is_err());
-        assert!("a11".parse::<Square>().is_err());
+        assert!("a9".parse::<Square>().is_err());
         assert!("b-1".parse::<Square>().is_err());
         assert!("a 1".parse::<Square>().is_err());
         assert!("".parse::<Square>().is_err());

core/src/coordinates/wings.rs

@@ -0,0 +1,22 @@
+// Eryn Wells <eryn@erynwells.me>
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum Wing {
+    KingSide = 0,
+    QueenSide = 1,
+}
+
+impl Wing {
+    pub const NUM: usize = 2;
+    pub const ALL: [Wing; Self::NUM] = [Self::KingSide, Self::QueenSide];
+}
+
+impl std::fmt::Display for Wing {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Wing::KingSide => write!(f, "kingside"),
+            Wing::QueenSide => write!(f, "queenside"),
+        }
+    }
+}

core/src/lib.rs

@@ -8,6 +8,6 @@ pub mod shapes;
 mod macros;
 
 pub use colors::Color;
-pub use coordinates::{Direction, File, Rank, Square};
+pub use coordinates::{Direction, File, Rank, Square, Wing};
 pub use pieces::{Piece, PlacedPiece};
 pub use shapes::Shape;