Floss: Add wbs support to adapter API

This patch adds the is_wbs_supported dbus method to the adapter.
It queries the get_wbs_supported method in IBluetooth.

Bug: 244507283
Tag: #floss
Test: ./build.py --target test
Test: Manual - Run btclient on a brya/gimble.
      bluetooth> adapter show
      ...
      btclient:info: IsWbsSupported: true
      ...

Change-Id: I2896a56b6b0753c3f38cb35c161997c3b6b019e7