[RESTRICT AUTOMERGE][pm] still allow debuggable for system app downgrades

Turns out we do have internal tests that downgrades system apps, so adding this exception to allow for that.

BUG: 267232653
BUG: 256202273

Test: manual
Change-Id: Ie281bbdc8788ee64ff99a7c5150da7ce7926235e
(cherry picked from commit ceeca68b8c)

services/core/java/com/android/server/pm/PackageManagerService.java

@@ -26757,10 +26757,13 @@ public class PackageManagerService extends IPackageManager.Stub
                     if (disabledPs != null) {
                         dataOwnerPkg = disabledPs.getPkg();
                     }
+                    if (!Build.IS_DEBUGGABLE && !dataOwnerPkg.isDebuggable()) {
+                        // Only restrict non-debuggable builds and non-debuggable version of the app
                         try {
                             checkDowngrade(dataOwnerPkg, pkgLite);
                         } catch (PackageManagerException e) {
-                        String errorMsg = "System app: " + packageName + " cannot be downgraded to"
+                            String errorMsg = "System app: " + packageName
+                                    + " cannot be downgraded to"
                                     + " older than its preloaded version on the system image. "
                                     + e.getMessage();
                             Slog.w(TAG, errorMsg);
@@ -26769,6 +26772,7 @@ public class PackageManagerService extends IPackageManager.Stub
                     }
                 }
             }
+        }
         return PackageManager.INSTALL_SUCCEEDED;
     }