Hide system apps until installed (1/2)

Applying this mechanism for system carrier apps to make visibility
reasonable from the user's perspective. In other words, before
hidden system apps have been installed, they wouldn't be listed
via APIs in PackageManager which are used at all apps list and
search in Settings and so on.

Test: atest CarrierAppUtilsTest
Test: atest PackageManagerTest
Test: cts DeviceOwnerTest
Test: gts ManagedProfileProvisioningHostsideTest
Bug: 74068582
Change-Id: I1f23aba589b98351a1871a44a3058b67c416f351
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index e33ecb8..44bdafe 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -3037,6 +3037,15 @@
     <permission android:name="android.permission.INSTALL_PACKAGE_UPDATES"
         android:protectionLevel="signature|privileged" />
 
+    <!-- Allows an application to install existing system packages. This is a limited
+         version of {@link android.Manifest.permission#INSTALL_PACKAGES}.
+         <p>Not for use by third-party applications.
+         TODO(b/80204953): remove this permission once we have a long-term solution.
+         @hide
+    -->
+    <permission android:name="com.android.permission.INSTALL_EXISTING_PACKAGES"
+        android:protectionLevel="signature|privileged" />
+
     <!-- @SystemApi Allows an application to clear user data.
          <p>Not for use by third-party applications
          @hide