Add Network Security Config file (fixes facebook#22375) (facebook#23105)

Summary:
This fixes facebook#22375. Android API level 28 and above now blocks all [clear text requests](https://developer.android.com/training/articles/security-config#CleartextTrafficPermitted) unless a network configuration rule is added to exclude it specifically.

The packager falls into this category and therefore gets blocked; resulting in the app being unable to connect to it.

Domains/IPs for the config have been taken from [here](https://github.com/facebook/react-native/blob/master/ReactAndroid/src/main/java/com/facebook/react/modules/systeminfo/AndroidInfoHelpers.java#L20-L22).

This change only adds to DevSupport android resources - so won't affect builds without DevSupport, e.g. release builds.

Changelog:
----------

[ANDROID] [DevSupport] add Network Security Config file to allow access to packager via cleartext requests in Android API 28 and above. (fixes facebook#22375)
Pull Request resolved: facebook#23105

Differential Revision: D13781516

Pulled By: cpojer

fbshipit-source-id: f7574f3e1b0fe6984efe1d0598ef631385c245bc

ReactAndroid/src/main/res/devsupport/xml/network_security_config.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<network-security-config>
+  <domain-config cleartextTrafficPermitted="true">
+    <domain includeSubdomains="false">localhost</domain>
+    <domain includeSubdomains="false">10.0.2.2</domain>
+    <domain includeSubdomains="false">10.0.3.2</domain>
+  </domain-config>
+</network-security-config>