Android: Move InstallWAD to a new WiiUtils class

I'm trying to move away from dumping every native method
in NativeLibrary.

Source/Android/jni/WiiUtils.cpp

@@ -0,0 +1,22 @@
+// Copyright 2021 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <string>
+
+#include <jni.h>
+
+#include "jni/AndroidCommon/AndroidCommon.h"
+
+#include "Core/WiiUtils.h"
+
+extern "C" {
+
+JNIEXPORT jboolean JNICALL Java_org_dolphinemu_dolphinemu_utils_WiiUtils_installWAD(JNIEnv* env,
+                                                                                    jclass,
+                                                                                    jstring jFile)
+{
+  const std::string path = GetJString(env, jFile);
+  return static_cast<jboolean>(WiiUtils::InstallWAD(path));
+}
+}