Make Melda VST plug-in UI work on macOS

[Paul-Licameli]

Your idea

Melda plug-ins, VST version, used to work in old 32-bit Audacity builds, but not longer work in version 2.3.1 or later.

To restore that requires non-obvious source code changes to use totally different SDKs

Problem to be solved

More third party plug-ins will be usable

Prior art

There may be clues to how to solve this in this open source project, specifically in this file, whose commit history contains code similar to what is in Audacity now, but it has been rewritten (I found it googling for hasCockosViewAsConfig)

https://github.com/juce-framework/JUCE/blob/master/modules/juce_audio_processors/format_types/juce_VSTPluginFormat.cpp

Additional context

No response