Ramping Apple Effects parameters doesn't change the parameter at all

[eljeff]

Here is code to show that using LowPassFilter.$cutoffFrequency.ramp(to: value, duration: someTime) has no effect on the actual filter.cutoffFrequency

I put this code in GenericNodeTests.swift

func testLowpass() {
    let engine = AudioEngine()
    let url = Bundle.module.url(forResource: "12345", withExtension: "wav", subdirectory: "TestResources")!
    let input = AudioPlayer(url: url)!
    let effect = LowPassFilter(input)
    engine.output = effect
    let startFreq: Float = 100
    let targetFreq: Float = 1000
    let rampDuration: Float = 0.1
    effect.cutoffFrequency = startFreq
    effect.$cutoffFrequency.ramp(to: targetFreq, duration: rampDuration)
    let audio = engine.startTest(totalDuration: 1.0)
    input.start()
    audio.append(engine.render(duration: 1.0))
    testMD5(audio)
    XCTAssertEqual(effect.cutoffFrequency, targetFreq)
}

[aure]

This seems to be true for all the Apple effects. Delay, Distortion, etc. all of the ones that come with the regular AudioKit swift package.

[aure]

Add a warning when trying to ramp a parameter that is intrinsically not rampable. Apple should be made aware of this limitation so I've added this as one of the radars we should file with them: #2570