Floss: Rename BluetoothQA to BluetoothQALegacy

Rename BluetoothQA to BluetoothQALegacy to prevent conflict name in the
next patch.

The legacy interface shall be removed after migrating all methods to the
new interface.

Bug: 261143122
Test: build locally
Tag: #floss

Change-Id: Id10e9f702b3f9df97137b039007d95a136977a8a