Using a probe connection to determine adapter msbc capability causes
problems on some adapters (ff8c3d2, 84bc0490a5, 717004334b,
pipewire#2030) and seems to be a bad idea.
Go back to probing for transparent msbc transport capability via HCI
commands. bluetooth/hci.h may be deprecated later, but for now it's
better to go back to using it. (In practice, adapters not supporting
esco appear to be fairly rare; kernel commit in 2013 refers to "older
devices", so if we can't use HCI, assume the adapter supports the
necessary modes.)
