Add SpaLib for Settings

SPA main activity can be launched by:
adb shell am start com.android.settings/.spa.SpaActivity

Bug: 235727273
Test: Manual launch SPA main activity
Change-Id: I7b196b0169f91732a6b37ff53a3f79b54267d93f

src/com/android/settings/spa/SpaActivity.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.spa
+
+import com.android.settingslib.spa.framework.BrowseActivity
+
+class SpaActivity : BrowseActivity(settingsPageProviders)