DPMS: add permission check to getDeviceOwnerLockScreenInfo()

The public API DPMS.getDeviceOwnerLockScreenInfo() currently doesn't
require any permission, as it doesn't check for one itself, and it uses
ILockSettings.getString() which doesn't check for a permission either.

We're fixing ILockSettings.getString() to check for
ACCESS_KEYGUARD_SECURE_STORAGE.  Therefore, to keep
DPMS.getDeviceOwnerLockScreenInfo() working for DPCs, make it explicitly
check for the device or profile owner before calling into ILockSettings
with a cleared calling identity.

Note, this is the same permission check that
DPMS.setDeviceOwnerLockScreenInfo() does.

Bug: 256170784
Test: m cts && atest com.android.cts.devicepolicy.MixedDeviceOwnerTest#testLockScreenInfo
Change-Id: Ic81d04b7c3746fa2da65f932ca28cb852fdeccb8

services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java

@@ -9321,7 +9321,11 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
 
     @Override
     public CharSequence getDeviceOwnerLockScreenInfo() {
-        return mLockPatternUtils.getDeviceOwnerInfo();
+        final CallerIdentity caller = getCallerIdentity();
+        Preconditions.checkCallAuthorization(
+                isDefaultDeviceOwner(caller) || isProfileOwnerOfOrganizationOwnedDevice(caller));
+        return mInjector.binderWithCleanCallingIdentity(() ->
+            mLockPatternUtils.getDeviceOwnerInfo());
     }
 
     private void clearUserPoliciesLocked(int userId) {