Create a Debug manifest inside React Native Android (#37771)

Summary:
Pull Request resolved: facebook/react-native#37771

While working on debugging tools, I noticed that we ask in every template app to
- Add a "com.facebook.react.devsupport.DevSettingsActivity" activity
- Add the <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>

This is error prone and can be cleanup as we now distribute React Native that is variant aware (debug/release).
So I'm creating a manifest inside `src/debug` that contains those directive so we don't need to ask users
to add them (I'm removing them from the template).

Changelog:
[Internal] [Changed] - Create a Debug manifest inside React Native Android

Reviewed By: cipolleschi

Differential Revision: D46556884

fbshipit-source-id: 10034a6b245bf419dfa663bc998c4d1ad5d24a90

Original-Commit: facebook/react-native@f3c8636

template/android/app/src/debug/AndroidManifest.xml

@@ -2,12 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
-    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
-
     <application
         android:usesCleartextTraffic="true"
         tools:targetApi="28"
-        tools:ignore="GoogleAppIndexingWarning">
-        <activity android:name="com.facebook.react.devsupport.DevSettingsActivity" android:exported="false" />
-    </application>
+        tools:ignore="GoogleAppIndexingWarning"/>
 </manifest>