[RF] AquaMai configuration refactor (#82)

更新了配置文件格式，原有的配置文件将被自动无缝迁移，详情请见新的配置文件中的注释（例外：`SlideJudgeTweak` 不再默认启用）
旧配置文件将被重命名备份，如果更新到此版本遇到 Bug 请联系我们

Updated configuration file schema. The old config file will be migrated automatically and seamlessly. See the comments in the new configuration file for details. (Except for `SlideJudgeTweak` is no longer enabled by default)
Your old configuration file will be renamed as a backup. If you encounter any bug with this version, please contact us.

AquaMai/AquaMai.Config.HeadlessLoader/ConfigAssemblyLoader.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using Mono.Cecil;
+
+namespace AquaMai.Config.HeadlessLoader;
+
+class ConfigAssemblyLoader
+{
+    public static Assembly LoadConfigAssembly(AssemblyDefinition assembly)
+    {
+        var references = assembly.MainModule.AssemblyReferences;
+        foreach (var reference in references)
+        {
+            if (reference.Name == "mscorlib" || reference.Name == "System" || reference.Name.StartsWith("System."))
+            {
+                reference.Name = "netstandard";
+                reference.Version = new Version(2, 0, 0, 0);
+                reference.PublicKeyToken = null;
+            }
+        }
+
+        var targetFrameworkAttribute = assembly.CustomAttributes.FirstOrDefault(attr => attr.AttributeType.Name == "TargetFrameworkAttribute");
+        if (targetFrameworkAttribute != null)
+        {
+            targetFrameworkAttribute.ConstructorArguments.Clear();
+            targetFrameworkAttribute.ConstructorArguments.Add(new CustomAttributeArgument(
+                assembly.MainModule.TypeSystem.String, ".NETStandard,Version=v2.0"));
+            targetFrameworkAttribute.Properties.Clear();
+            targetFrameworkAttribute.Properties.Add(new Mono.Cecil.CustomAttributeNamedArgument(
+                "FrameworkDisplayName", new CustomAttributeArgument(assembly.MainModule.TypeSystem.String, ".NET Standard 2.0")));
+        }
+
+        var stream = new MemoryStream();
+        assembly.Write(stream);
+        FixLoadedAssemblyResolution();
+        return AppDomain.CurrentDomain.Load(stream.ToArray());
+    }
+
+    private static bool FixedLoadedAssemblyResolution = false;
+
+    // XXX: Why, without this, the already loaded assemblies are not resolved?
+    public static void FixLoadedAssemblyResolution()
+    {
+        if (FixedLoadedAssemblyResolution)
+        {
+            return;
+        }
+        FixedLoadedAssemblyResolution = true;
+
+        var loadedAssemblies = new Dictionary<string, Assembly>();
+        foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
+        {
+            loadedAssemblies[assembly.FullName] = assembly;
+        }
+
+        AppDomain.CurrentDomain.AssemblyResolve += (sender, args) =>
+        {
+            if (loadedAssemblies.TryGetValue(args.Name, out var assembly))
+            {
+                return assembly;
+            }
+            return null;
+        };
+    }
+}