Adds caller check to getAllPackages()

This change enforces that only system, root or shell may call
getAllPackages(), a hidden API that shares all package names regardless
of user, instant app or package visibility rules.

Bug: 174661955
Test: 'adb shell pm compile -a -m speed' doesn't fail with
      SecurityException
Change-Id: I86a03c46896f21cdbeeda2af150675fe77d61955

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

@@ -8946,6 +8946,7 @@ public class PackageManagerService extends IPackageManager.Stub
 
     @Override
     public List<String> getAllPackages() {
+        enforceSystemOrRootOrShell("getAllPackages is limited to privileged callers");
         final int callingUid = Binder.getCallingUid();
         final int callingUserId = UserHandle.getUserId(callingUid);
         synchronized (mLock) {