Change cross user permission for MANAGE_DEVICE_POLICY_LOCK.

* Changing it from `MANAGE_DEVICE_POLICY_ACROSS_USERS_FULL` to
  `MANAGE_DEVICE_POLICY_ACROSS_USERS_SECURITY_CRITICAL`.
* `MANAGE_DEVICE_POLICY_ACROSS_USERS_FULL` is only for privacy intrusive policies, and locking the device is clearly not such policy and should be available to profile owners as well.

Test: btest android.devicepolicy.cts.LockTest with feature flag
on/off
Bug: 378882674
Bug: 336297680
Flag: android.app.admin.flags.lock_now_coexistence

Change-Id: I52c23f0a0d0e419fd172e19aef3a862c57f25e6b