Add Bluetooth Slice

Bluetooth slice is added a special case, due to the migration of
bluetooth to a Switch Bar instead of a preference with a controller.

Change-Id: I8b70bb66c862255a4e8d2426ac09939ba6197624
Merged-In: Icfdcd77601ad1e64e0f6c352a8d691f0181515c8
Fixes: 67997327
Test: robotests

tests/robotests/src/com/android/settings/wifi/WifiSliceBuilderTest.java

@@ -68,7 +68,7 @@ public class WifiSliceBuilderTest {
     }
 
     @Test
-    public void getWifiSlice_correctData() {
+    public void getWifiSlice_correctSliceContent() {
         final Slice wifiSlice = WifiSliceBuilder.getSlice(mContext);
         final SliceMetadata metadata = SliceMetadata.from(mContext, wifiSlice);