Revert "cmake build system: don't add NovaUGens to plugin dirs extra"

This reverts commit 6fed081dcd422839cdde94d9e9aa9a09407a4007.
nova ugens: move interpolators to separate header file

Signed-off-by: Tim Blechmann <tim@klingt.org>
NovaUGens - cast floating-point constants to Float

Signed-off-by: Tim Blechmann <tim@klingt.org>
NovaUGens: implement high-precision oscillators

Signed-off-by: Tim Blechmann <tim@klingt.org>