Add .aupreset support

[rhelsing]

#160

Getting started, feedback would be appreciated on next steps! @emilio1234 @psobot

[psobot]

I don't know that this will work - the JUCE code doesn't seem to have a setPreset method on AudioUnitClient:

    struct AudioUnitClient
    {
        virtual ~AudioUnitClient() = default;
        virtual AudioUnit getAudioUnitHandle() const noexcept = 0;
    };

[0xdevalias]

Older thread:

• https://forum.juce.com/t/loading-audiounit-preset/31756

And more specific feature request thread that I just opened for this:

• https://forum.juce.com/t/add-getpreset-setpreset-to-audiounitclient/61430/2

[0xdevalias]

Related technical docs:

• https://developer.apple.com/documentation/audiotoolbox/auaudiounitpreset

  • AUAudioUnitPreset

  • The AUAudioUnitPreset class describes an interface for custom parameter settings provided by the audio unit developer. These presets often produce a useful sound or starting point.

  • For more details on working with Audio Unit presets, see Audio Units - How to correctly save and restore Audio Unit presets. Note that the version 3 fullState property is bridged to the version 2 kAudioUnitProperty_ClassInfo API. Similarly, the version 3 fullStateForDocument property is bridged to the version 2 kAudioUnitProperty_ClassInfoFromDocument API.

• https://developer.apple.com/library/archive/technotes/tn2157/_index.html

  • Technical Note TN2157
    Audio Units - How to correctly save and restore Audio Unit presets.