Restrict Hotspot tile in Quick Settings

- Disable Hotspot tile when user is not allowed to enable Wi-Fi tethering.

- Show restriction message in Hotspot tile secondary label.

Bug: 203168953
Test: manual test
atest -c com.android.systemui.qs.tiles.HotspotTileTest

Change-Id: Ibe8f1824090dacb1aa03b116adcd2ae5e7ea2892