Add experimental RA procedural map generator

Add an experimental procedural map generator for the Red Alert mod,
along with supporting code that may assist in the development of map
generators for other mods.

Map generation may be accessed as a tool in the Map Editor. This change
does not presently introduce direct lobby options for generated maps.

Features:

- Terrain with land, water, beaches, cliffs, roads, debris, and trees.
- Placement of mpspawns, neutral buildings, and resources.
- Rotational and mirror symmetry options.
- Various configurable parameters with presets.
- Deterministic with configurable seed.
- Performant.

OpenRA.Mods.Common/Widgets/Logic/Editor/MapToolsLogic.cs

@@ -10,7 +10,9 @@
 #endregion
 
 using System.Collections.Generic;
+using System.Linq;
 using OpenRA.Graphics;
+using OpenRA.Mods.Common.Traits;
 using OpenRA.Widgets;
 
 namespace OpenRA.Mods.Common.Widgets.Logic
@@ -19,16 +21,20 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 	{
 		[FluentReference]
 		const string MarkerTiles = "label-tool-marker-tiles";
+		[FluentReference]
+		const string MapGenerator = "label-tool-map-generator";
 
 		enum MapTool
 		{
-			MarkerTiles
+			MarkerTiles,
+			MapGenerator
 		}
 
 		readonly DropDownButtonWidget toolsDropdown;
 		readonly Dictionary<MapTool, string> toolNames = new()
 		{
-			{ MapTool.MarkerTiles, MarkerTiles }
+			{ MapTool.MarkerTiles, MarkerTiles },
+			{ MapTool.MapGenerator, MapGenerator }
 		};
 
 		readonly Dictionary<MapTool, Widget> toolPanels = new();
@@ -42,10 +48,17 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 			var markerToolPanel = widget.Get("MARKER_TOOL_PANEL");
 			toolPanels.Add(MapTool.MarkerTiles, markerToolPanel);
+			if (world.WorldActor.TraitsImplementing<IMapGenerator>().Any())
+			{
+				var mapGeneratorToolPanel = widget.GetOrNull("MAP_GENERATOR_TOOL_PANEL");
+				if (mapGeneratorToolPanel != null)
+					toolPanels.Add(MapTool.MapGenerator, mapGeneratorToolPanel);
+			}
 
 			toolsDropdown.OnMouseDown = _ => ShowToolsDropDown(toolsDropdown);
 			toolsDropdown.GetText = () => FluentProvider.GetMessage(toolNames[selectedTool]);
-			toolsDropdown.Disabled = true; // TODO: Enable if new tools are added
+			if (toolPanels.Count <= 1)
+				toolsDropdown.Disabled = true;
 		}
 
 		void ShowToolsDropDown(DropDownButtonWidget dropdown)
@@ -61,7 +74,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				return item;
 			}
 
-			var options = new[] { MapTool.MarkerTiles };
+			var options = new[] { MapTool.MarkerTiles, MapTool.MapGenerator };
 			dropdown.ShowDropDown("LABEL_DROPDOWN_TEMPLATE", 150, options, SetupItem);
 		}