Move DevSettingsActivity from main to debug (#28770)

Summary:
As described in DevSettingsActivity, it should be added to the apps
debug/ instead of main/ manifest.

## Changelog
Android Changed - Move DevSettingsActivity from `main` to `debug` manifest
Pull Request resolved: #28770

Test Plan: Tested locally by building example app

Differential Revision: D21281922

Pulled By: shergin

fbshipit-source-id: ec4dc7c0ac54367aa38cca5b4146ef71cf18b73b

Author: Your Name

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

@@ -4,5 +4,10 @@
 
     <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
 
-    <application android:usesCleartextTraffic="true" tools:targetApi="28" tools:ignore="GoogleAppIndexingWarning" />
+    <application
+        android:usesCleartextTraffic="true"
+        tools:targetApi="28"
+        tools:ignore="GoogleAppIndexingWarning">
+        <activity android:name="com.facebook.react.devsupport.DevSettingsActivity" />
+    </application>
 </manifest>

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

@@ -21,7 +21,5 @@
             <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
       </activity>
-      <activity android:name="com.facebook.react.devsupport.DevSettingsActivity" />
     </application>
-
 </manifest>