Add unlock to see more messaging to locked shade

If the device is locked, and there are no notifications visible on the
keyguard, and the user expands the shade, if there would be
notifications present if the device is unlocked, then display a message.

Test: manual
      1: Enable "Only Show Unseen Notifs On Keyguard" flag
      2: Have some notifications
      3: Lock device
      4: On keyguard, observe no notifications
      5: Expand shade (without unlocking)
      Observe: New UI treatment is visible
Bug: 240472040
Change-Id: Ieeeb12aabb2b07bd9f4156a000ef8b2659be5e2f