Bump NetworkStack to SDK 31

 - Set build SDK to module_31 instead of system_30 in release
   target
 - Set target SDK to 31 in release target instead of 30
 - Update version codes as per convention
 - Move "current" shim library to api31 shims
 - Add new "current" shim library for next development SDK

Ignore-AOSP-First: SDK 31 does not exist in AOSP. Will be partially
                   cherry-picked.

Bug: 189581241
Test: atest NetworkStackTests NetworkStackNextTests \
        CtsNetTestCasesLatestSdk

Change-Id: Ia55598123a5d4432464e9d1b1c637e9e0b58dd8e
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 55357a8..6a11b2c 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -19,8 +19,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.android.networkstack"
   android:sharedUserId="android.uid.networkstack"
-  android:versionCode="309999900"
-  android:versionName="r_aml_309999900"
+  android:versionCode="319999900"
+  android:versionName="s_aml_319999900"
 >
     <!-- Permissions must be defined here, and not in the base manifest, as the network stack
          running in the system server process does not need any permission, and having privileged