[QS] Disable hotspot when data saver is enabled

Added new callback for data saver and used the data saver enabled state
to determine whether the tile was available (similar to how airplane
mode works).

Test: Visually (via toggling both data saver/hotspot tiles)
Bug: 33003328
Change-Id: I0b0e5e382ab2a9ee13d4412ed059c523795b68c7