The BluetoothDevicePreference need to know whether to display with an
invalid name. However pass in the whole fragment is over-killing.
This cl decouple it for several reasons:
1. In P, BluetoothDevicePreference will be used in other fragment.
2. In preference lifecycle from end user side, this flag is constant.
Bug: 69333961
Test: RunSettingsRoboTests
Change-Id: I3dbcd2a4aafa3ead74371534250e5e7c3ee221f7
cf1ce05ce5