Use test stubs for RollbackTests, not system stubs.

Adds @TestApi for all system apis needed for RollbackTests.

Removes @SystemApi for RollbackManager.expireRollbackForPackage and
RollbackManager.reloadPersistedData, which were always intended to be
used solely for testing.

Bug: 127282563
Test: atest RollbackTest StagedRollbackTest
Change-Id: I183b8a484b4a08f36fc19d64241ab408d28c64ca
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index d176260..85cdbb1 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -2524,7 +2524,7 @@
     <permission android:name="android.permission.WRITE_GSERVICES"
         android:protectionLevel="signature|privileged" />
 
-    <!-- @SystemApi @hide Allows an application to modify config settings.
+    <!-- @SystemApi @TestApi @hide Allows an application to modify config settings.
     <p>Not for use by third-party applications. -->
     <permission android:name="android.permission.WRITE_DEVICE_CONFIG"
         android:protectionLevel="signature|configurator"/>
@@ -3917,7 +3917,7 @@
     <permission android:name="android.permission.PACKAGE_ROLLBACK_AGENT"
         android:protectionLevel="signature" />
 
-    <!-- @SystemApi @hide Allows managing apk level rollbacks. -->
+    <!-- @SystemApi @TestApi @hide Allows managing apk level rollbacks. -->
     <permission android:name="android.permission.MANAGE_ROLLBACKS"
         android:protectionLevel="signature|verifier" />