Instruments: Have the Zynaddsubfx UI embed like VST(i) plugins

Enhancement Summary

You can see a setting for embedding VST(i) plugins into the LMMS editor itself, so you can use it without it spawning a new window. can't we do that with zynaddsubfx?

Implementation Details / Mockup

Perhaps using the QT embedding thing or win32, i dont know.

A mock up

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