improve Android Network Security config (facebook#23429)

Summary:
This PR is trying to improve Android Network Security configuration introduced in facebook@84572c4. I found that Android merges all manifest files into a single manifest file when building an app, so this PR provides AndroidManifest.xml with network security config in debug folder, that will be used only for debug builds. Also the network security configuration will be applied to only app that target API 28. Moved security config file to xml-v28, so that it'll only visible to API 28 and above.

See https://developer.android.com/studio/build/manifest-merge

[Android] [Changed] -  Android Network Security configuration.
Pull Request resolved: facebook#23429

Differential Revision: D14065124

Pulled By: cpojer

fbshipit-source-id: 0f5ac5addbe968ed7e5cb57f356e2572de2690a8

Author: dulmandakh

local-cli/templates/HelloWorld/android/app/src/main/AndroidManifest.xml

@@ -1,5 +1,4 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-  xmlns:tools="http://schemas.android.com/tools"
   package="com.helloworld">
 
     <uses-permission android:name="android.permission.INTERNET" />
@@ -11,9 +10,7 @@
       android:icon="@mipmap/ic_launcher"
       android:roundIcon="@mipmap/ic_launcher_round"
       android:allowBackup="false"
-      android:theme="@style/AppTheme"
-      android:networkSecurityConfig="@xml/network_security_config"
-      tools:ignore="GoogleAppIndexingWarning,UnusedAttribute">
+      android:theme="@style/AppTheme">
       <activity
         android:name=".MainActivity"
         android:label="@string/app_name"

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

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+    <application tools:targetApi="28" tools:ignore="GoogleAppIndexingWarning" android:networkSecurityConfig="@xml/react_native_config" />
+</manifest>