lineage-sdk: Bring back Lineage resources to system

This partially reverts commit 4068ca7095.

Reason for revert:
* Currently Android (PackageManagerService) scans for packages (APKs)
  only in ANDROID_ROOT/framework/ along the standard
  $partition/{app,priv-app} directories.

* By moving to system_ext we accidentally broke the addition of
  AndroidManifest entries to the runtime (resources and assets weren't
  affected as handled manually/differently).
  Note: jars can still be loaded with no issues from this partition.

* Instead of allowing system_ext to provide framework packages and
  pending (future) AOSP discussion to include system_ext to the allowed
  path, simply move back the package.

Change-Id: I352c1518ed43e0631abaebccc1e2093b09d49b6f

Android.bp

@@ -18,7 +18,6 @@ android_app {
     name: "org.lineageos.platform-res",
     sdk_version: "core_platform",
     certificate: "platform",
-    system_ext_specific: true,
 
     manifest: "lineage/res/AndroidManifest.xml",