[explorer, moves, position] Implement a moves command in explorer

The moves command writes all possible moves to the terminal.

Move the previous implementation of the moves command, which marked squares that
a piece could move to, to a 'movement' command.

moves/src/generators.rs

@@ -16,12 +16,20 @@ pub use pawn::PawnMoveGenerator;
 pub use slider::{BishopMoveGenerator, QueenMoveGenerator, RookMoveGenerator};
 
 use crate::Move;
+use chessfriend_core::Square;
 
 #[derive(Clone, Debug, Eq, Hash, PartialEq)]
 pub struct GeneratedMove {
     pub(crate) ply: Move,
 }
 
+impl GeneratedMove {
+    #[must_use]
+    pub fn origin(&self) -> Square {
+        self.ply.origin_square()
+    }
+}
+
 impl std::fmt::Display for GeneratedMove {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         self.ply.fmt(f)