Actually fix GenOrderedControls invariant, dropping Libretro hack

fixes a836884 and 3384ce8

src/BizHawk.Client.Common/display/InputDisplayGenerator.cs

@@ -16,15 +16,9 @@ public static string Generate(IController source)
 				throw new InvalidOperationException("Can't generate input display string with empty mnemonics cache");
 
 			var sb = new StringBuilder();
-			var controls = source.Definition.ControlsOrdered.ToList();
-			// index 0 is for controls that don't belong to any indexed player
-			if (controls.ElementAtOrDefault(0) != null)
-			{
-				controls.Add(controls[0]);
-				controls.RemoveAt(0);
-			}
-
-			foreach ((string buttonName, AxisSpec? axisSpec) in controls.SelectMany(x => x))
+			var players = source.Definition.ControlsOrdered;
+			var playersNewOrder = players.Skip(1).Concat(players.Take(1)); // move first ("player 0") to end
+			foreach ((string buttonName, AxisSpec? axisSpec) in playersNewOrder.SelectMany(static x => x))
 			{
 				if (axisSpec.HasValue)
 				{

src/BizHawk.Emulation.Common/Base Implementations/ControllerDefinition.cs

@@ -114,6 +114,7 @@ private void AssertMutable()
 			if (!_mutable) throw new InvalidOperationException(ERR_MSG);
 		}
 
+		/// <remarks>implementors should include empty lists for empty players, including "player 0", to match this base implementation</remarks>
 		protected virtual IReadOnlyList<IReadOnlyList<(string Name, AxisSpec? AxisSpec)>> GenOrderedControls()
 		{
 			var ret = new List<(string, AxisSpec?)>[PlayerCount + 1];

src/BizHawk.Emulation.Cores/Libretro/Libretro.IEmulator.cs

@@ -111,29 +111,6 @@ public LibretroControllerDef()
 
 				MakeImmutable();
 			}
-
-			protected override IReadOnlyList<IReadOnlyList<(string Name, AxisSpec? AxisSpec)>> GenOrderedControls()
-			{
-				// all this is to remove the keyboard buttons from P0 and put them in P3 so they appear at the end of the input display
-				var players = base.GenOrderedControls().ToList();
-				List<(string, AxisSpec?)> retroKeyboard = new();
-				var p0 = (List<(string, AxisSpec?)>) players[0];
-				for (var i = 0; i < p0.Count; /* incremented in body */)
-				{
-					(string ButtonName, AxisSpec?) button = p0[i];
-					if (CategoryLabels.TryGetValue(button.ButtonName, out var v) && v is CAT_KEYBOARD)
-					{
-						retroKeyboard.Add(button);
-						p0.RemoveAt(i);
-					}
-					else
-					{
-						i++;
-					}
-				}
-				players.Add(retroKeyboard);
-				return players;
-			}
 		}
 
 		public ControllerDefinition ControllerDefinition { get; }