[core] Make `Services.registerAsOverride` public to be used in tests

mirai-core-utils/src/commonMain/kotlin/Services.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019-2022 Mamoe Technologies and contributors.
+ * Copyright 2019-2023 Mamoe Technologies and contributors.
  *
  * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
  * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
@@ -36,7 +36,7 @@ public object Services {
         }
     }
 
-    internal fun registerAsOverride(baseClass: String, implementationClass: String, implementation: () -> Any) {
+    public fun registerAsOverride(baseClass: String, implementationClass: String, implementation: () -> Any) {
         lock.withLock {
             overrided[baseClass] = Implementation(implementationClass, lazy(implementation))
         }