Mark NetworkStack as coreApp

Packages marked as coreApp will be included in the parsed packages when
booting in encrypted or encrypting state, on legacy devices (upgrading
from P) that support FDE, not FBE.

This fixes a bug on such devices where the system server cannot load
because of the missing NetworkStack.

Bug: 197282772
Test: Installed updated app on device, booted, checked connectivity,
      verified that PackageInfo has coreApp=true.
Change-Id: I0887b14819654f2c14501f78bfe5bc61d062dcf9
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 6a11b2c..8750795 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -21,6 +21,7 @@
   android:sharedUserId="android.uid.networkstack"
   android:versionCode="319999900"
   android:versionName="s_aml_319999900"
+  coreApp="true"
 >
     <!-- 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