Partial PackfileVFS port

Partially ported PackfileVFS from the C++ version. Will implement the rest of it when it's needed. Just using the existing behavior for now. Will rewrite it in the near future since it's not sufficient for Nanoforge anymore.

Author: Moneyl

src/FileSystem/PackfileVFS.bf

@@ -0,0 +1,56 @@
+using System.Collections;
+using RfgTools.Formats;
+using Nanoforge;
+using System.IO;
+using System;
+
+namespace Nanoforge.FileSystem
+{
+    ///RFG packfile interface
+    ///NOTE: This API sucks and will be rewritten in the near future. It's a port from the C++ version. This was originally written when Nanoforge was just a file viewer.
+    ///      It's insufficient for the new goals of Nanoforge of being a full modding suite. It will be rewritten after adding the map editor, but before adding other features.
+    ///      I'm using the existing code initially to save time. I want to get the rewrite public ASAP so improvements to the map editor can be started again.
+    ///      Doing all the code rewrites up front would likely delay that by months. It's better to get early feedback IMO.
+	public static class PackfileVFS
+	{
+        private static String _dataFolder = new .() ~delete _;
+        public static List<PackfileV3> Packfiles = new .() ~DeleteContainerAndItems!(_);
+
+        ///Scan all packfiles in the data folder
+        public static void SetDataFolder(StringView dataFolderPath)
+        {
+            if (!Directory.Exists(dataFolderPath))
+			{
+                //TODO: Add error logging here
+                return;
+            }
+
+            //Clear packfiles
+            _dataFolder.Set(dataFolderPath);
+            ClearAndDeleteItems(Packfiles);
+
+            //Scan headers of packfiles in new data folder
+            for (var file in Directory.EnumerateFiles(_dataFolder))
+            {
+                if (file.GetExtension(.. scope .()) != ".vpp_pc")
+                    continue;
+
+                String filePath = file.GetFilePath(.. scope .());
+                PackfileV3 packfile = new .(filePath);
+                if (packfile.ReadMetadata() case .Err(let err))
+                {
+                    delete packfile;
+                    Runtime.FatalError(scope $"Failed to read packfile. Error: '{err}'"); //TODO: Add proper error logging instead of crashing
+                    continue;
+                }
+                if (packfile.ReadAsmFiles() case .Err(let err))
+                {
+                    delete packfile;
+                    Runtime.FatalError(scope $"Failed to read asm_pc file in packfile. Error: '{err}'"); //TODO: Add proper error logging instead of crashing
+                    continue;
+                }
+                Packfiles.Add(packfile);
+            }
+        }
+	}
+}