This is a squashed commit featuring the following:
Connect:
- Synchronize player volume with mixer volume on playback
- Fix step size on volume up/down events
- Remove no-op mixer started/stopped logic
Playback:
- Move from `connect` to `playback` crate
- Make cubic volume control available to all mixers with `--volume-ctrl cubic`
- Normalize volumes to `[0.0..1.0]` instead of `[0..65535]` for greater precision and performance (breaking)
- Add `--volume-range` option to set dB range and control `log` and `cubic` volume control curves
- Fix `log` and `cubic` volume controls to be mute at zero volume
Alsa mixer:
- Complete rewrite (breaking)
- Query card dB range for the `log` volume control unless specified otherwise
- Query dB range from Alsa softvol (previously only from hardware)
- Use `--device` name for `--mixer-card` unless specified otherwise
- Fix consistency for `cubic` between cards that report minimum volume as mute, and cards that report some dB value
- Fix `--volume-ctrl {linear|log}` to work as expected
- Removed `--mixer-linear-volume` option; use `--volume-ctrl linear` instead
