Show connecting hearing devices in A11y hearing devices page

We only show connected hearing devices in the hearing devices page now.
When user pairing a device from pairing page and back to the hearing
devices page after the device is bonded, it's confusing no device shown
in the list because the device is still connecting to profiles. We
should show the connecting device to avoid confusion.

Bug: 283268686
Test: make RunSettingsRoboTests ROBOTEST_FILTER=DeviceListPreferenceFragmentTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=AvailableHearingDeviceUpdaterTest
Change-Id: Id3b29c12b80c282736a3e6ca73bcf317e0652b89
Merged-In: Id3b29c12b80c282736a3e6ca73bcf317e0652b89