Floss: propagate wbs_supported to BluetoothMedia directly

Currently wbs_supported is stored in hfp_shim in a way that could cause
troubles in a multi-device setting due to sharing a dirty state.

In this CL, we remove that storage and propagate wbs_supported to
BluetoothMedia directly.

Also, we will assume that the device supports CVSD as soon as the SLC is
established, since NBS-only devices may not support codec-negotiation
and there will be no caller to pass that information.

Bug: 241014631
Tag: #floss
Test: Build and verify wbs_supported is correctly exposed
Change-Id: I95e76895c4974149bb97d03c90957ba293e1f169