USB MIDI: Rename as UsbAlsaMidiDevice

UsbMidiDevice is a confusing name for the ALSA MIDI path when
UsbDirectMidiDevice exists. This CL renames UsbMidiDevice as
UsbAlsaMidiDevice.

Bug: 266753421
Test: MIDI Keyboard and MIDI Scope
Change-Id: I6aca2b9c10043bcaa28fee1066cbece66578397a