Persist Bluetooth CoD config value across reboot

Create new Settings key for storage and update the API doc.

Bug: 36015415
Test: Verified by storing a value through a test app and restarting the
machine to ensure it's picked up.

Change-Id: I94aa054e525c4656bb3a824a29cae9c88f8904e0

core/java/android/bluetooth/BluetoothAdapter.java

@@ -1134,8 +1134,10 @@ public final class BluetoothAdapter {
     }
 
     /**
-     * Sets the {@link BluetoothClass} Bluetooth Class of Device (CoD) of
-     * the local Bluetooth adapter.
+     * Sets the {@link BluetoothClass} Bluetooth Class of Device (CoD) of the local Bluetooth
+     * adapter.
+     *
+     * <p>Note: This value persists across system reboot.
      *
      * @param bluetoothClass {@link BluetoothClass} to set the local Bluetooth adapter to.
      * @return true if successful, false if unsuccessful.

core/java/android/provider/Settings.java

@@ -7402,6 +7402,13 @@ public final class Settings {
          */
         public static final String AIRPLANE_MODE_TOGGLEABLE_RADIOS = "airplane_mode_toggleable_radios";
 
+        /**
+         * An integer representing the Bluetooth Class of Device (CoD).
+         *
+         * @hide
+         */
+        public static final String BLUETOOTH_CLASS_OF_DEVICE = "bluetooth_class_of_device";
+
         /**
          * A Long representing a bitmap of profiles that should be disabled when bluetooth starts.
          * See {@link android.bluetooth.BluetoothProfile}.