add support for a hybrid momentary/toggle patch type

[sean-e]

Someone on the Fractal forum requested a hybrid latching/momentary FC switch type:

I'd love to have a third in-between option which is a combination of latching and momentary, like the TC Electronics Spark Boost: it functions as a normal latching switch unless you hold it down for nnn milliseconds (say 800ms), at which point it becomes momentary and will release as soon as you let it go. You could globally set the engage delay time hard-coded or as a setting. Call it "Phrase Switching".

USE CASE: you have a block (boost, flanger, whatever) that you sometimes leave on, but that you also sometimes use in a momentary fashion. This feature makes that possible in an easy and intuitive way using a single switch. ATM, you need to burn two switches to achieve the same thing -- one latching and one momentary.

Issues: This would be incompatible with secondary functions; and there is the headache of axe-fx sync variations.

Implementation notes of the new patch type: In clean state, on button press assume momentary, check elapsed duration on release to potentially convert to toggle; if is toggle, then no longer clean once it becomes active; momentary state is always clean; disable of active toggle reverts to clean state.