Show meaningful value for effect parameters

[ronso0]

Feature Description

Example:
show actual Hz value for the low and high pass cutoff of the built-in filter effects

Good: Parametric EQ

mixxx/src/effects/backends/builtin/parametriceqeffect.cpp

Lines 54 to 63 in f96d168

	EffectManifestParameterPointer center1 = pManifest->addParameter();
	center1->setId("center1");
	center1->setName(QObject::tr("Center 1"));
	center1->setShortName(QObject::tr("Center 1"));
	center1->setDescription(QObject::tr(
	"Center frequency for Filter 1, from 100 Hz to 14 kHz"));
	center1->setValueScaler(EffectManifestParameter::ValueScaler::Logarithmic);
	center1->setUnitsHint(EffectManifestParameter::UnitsHint::Hertz);
	center1->setNeutralPointOnScale(0.5);
	center1->setRange(100, kDefaultCenter1, 14000);

Not so good: MoogLadder4Filter

mixxx/src/effects/backends/builtin/moogladder4filtereffect.cpp

Lines 5 to 6 in f96d168

	static constexpr double kMinCorner = 0.0003; // 13 Hz @ 44100
	static constexpr double kMaxCorner = 0.5; // 22050 Hz @ 44100

mixxx/src/effects/backends/builtin/moogladder4filtereffect.cpp

Lines 32 to 35 in f96d168

	lpf->setUnitsHint(EffectManifestParameter::UnitsHint::Unknown);
	lpf->setDefaultLinkType(EffectManifestParameter::LinkType::LinkedLeft);
	lpf->setNeutralPointOnScale(1);
	lpf->setRange(kMinCorner, kMaxCorner, kMaxCorner);

[ronso0]

Fixed by #11041 I think