Stages: add CV over the fader, as hardware

[pyerbass]

A trick with the hardware turns each segment in VCO, but can't be done in VCV

• set the segment in LFO - green looping mode
• set the fader at the top to have a C1 note
• Send a 1V/oct sequence in Time/level CV in, then the osc tracks up to C7

In the VCV version, the last point doesn't happen. CV doesn't go higher than the fader position

[UncleClapton]

In case this information becomes useful to anyone in the future,

I recently did some digging into Stages in attempts to better understand it, and I think the root cause is that Stages in Rack clamps the combined CV/Slider value to 0V - 1V.

AudibleInstruments/src/Stages.cpp

Line 225 in a1cd335

primaries[i] = clamp(params[LEVEL_PARAMS + i].getValue() + inputs[LEVEL_INPUTS + i].getVoltage() / 8.f, 0.f, 1.f);

In the Stages firmware, though, the comparable value is clamped to (effectively) -1V - +2V instead, https://github.com/pichenettes/eurorack/blob/08460a69a7e1f7a81c5a2abcc7189c9a6b7208d4/stages/cv_reader.cc#L77

#101 somewhat addresses this, but It doesn't seem like this is dependent on the mode of the channel, and is just standard behavior.