Updates to phetioFeatured

[arouinfar]

For #323

Due to changes made in https://github.com/phetsims/studio/issues/303 and https://github.com/phetsims/studio/issues/309, there are some additional elements we should make phetioFeatured: true so linked elements properly show up in the Featured tree.

• view.graphs.pedigreeNode.pedigreeGraphNode
• model.generationClock
• view.graphs.populationNode.populationModel <= This is a linked element, so model.graphs.populationModel is actually featured.
• view.graphs.populationNode.populationGraphNode.dataProbeNode
• model.graphs.populationModel.dataProbe
• model.graphs.proportionsModel

For consistency, I would also expect to see these things featured, and was surprised to find they weren't. @pixelzoom feel free to veto if you disagree.

• view.addMutationsPanel.visibleProperty
• view.graphs.populationNode.populationGraphNode.yZoomButtonGroup.visibleProperty
• model.graphs.populationModel.yZoomLevelProperty

I've requested that these elements be made phetioReadOnly: true in #344, so I recommend that we also make them phetioFeatured: false

• view.graphs.pedigreeNode.allelesPanel.*Row.checkbox.visibleProperty <= N/A, not longer instrumented, see Elements to make phetioReadOnly: true #344 (comment)
• view.graphs.populationNode.populationGraphNode.generationScroller.*Button.enabledProperty

[pixelzoom]

Done in the commits below. There were API changes, no migration rules.

A couple of deviations from what was requested:

• view.graphs.populationNode.populationModel is a linked element. So the element that is featured is actually model.graphs.populationModel.
• view.graphs.pedigreeNode.allelesPanel.*Row.checkbox.visibleProperty are no longer instrumented, so there's nothing to do for this.

@arouinfar please review. Close if OK.

[arouinfar]

Looks good @pixelzoom, thanks!