[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 ceeca68b8c3f0ed8427b0212f63defe2f075146e)
diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index 3f6087b..4655d09 100644
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -15003,15 +15003,19 @@
                         if (disabledPs != null) {
                             dataOwnerPkg = disabledPs.pkg;
                         }
-                        try {
-                            checkDowngrade(dataOwnerPkg, pkgLite);
-                        } catch (PackageManagerException e) {
-                            String errorMsg = "System app: " + packageName
-                                    + " cannot be downgraded to"
-                                    + " older than its preloaded version on the system image. "
-                                    + e.getMessage();
-                            Slog.w(TAG, errorMsg);
-                            return PackageHelper.RECOMMEND_FAILED_VERSION_DOWNGRADE;
+                        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"
+                                        + " older than its preloaded version on the system image. "
+                                        + e.getMessage();
+                                Slog.w(TAG, errorMsg);
+                                return PackageHelper.RECOMMEND_FAILED_VERSION_DOWNGRADE;
+                            }
                         }
                     }
                 }