[Marco-Farruggio]

As I code a keep a notepad window open and jot down anything I want to think about later, these were a few small tweaks which I've decided to squash into one PR

• Rename DeviceNotAvailable -> DeviceUnavailable:
  • Why?: Better English, less words, shorter, matches HostUnavailable
• Normalize thread names:
  • server clients: cpal_<host>_client_<pid>
  • worker threads: cpal_<host>_<dir>
• Remove unused frames_to_duration on Windows
  • Mentioned in: feat(pipewire,pulseaudio): name the application and its streams #1409
• Clean up From<ndk::audio::AudioError> for Error
• Clean up From<jack::Error> for Error
• Remove some extern crates
  • Why?: Legacy syntax, I've left some though for now, where it's not a super simple change (e.g., re-exporting)
• Move some duplicated duplex stream config validation into a new crate::duplex::validate_duplex_config
  • A New OSS Host for FreeBSD #1404 will also use this
  • Some hosts have host-specific requirements which make it more logical to write their own duplex config validation checks, instead of using duplex::validate_duplex_config then checking their own reqs.