Get rid of as unknown as Node in traits

[jessegreenberg]

In phetsims/joist#881 @samreid showed a way to get rid of the as unknown as Node for traits.

The way to make the type cast unecessary is to declare Node as the type for the constructor with

const Voicing = <SuperType extends Constructor<Node>>( Type: SuperType )

We should use that for other traits too!

I see this as unknown as Node in

• ParallelDOM - this isn't a trait anymore, but the type casts are still necessary because of old implementation that used to assume trait. Would be nice to get rid of someday, but its larger than this issue.
• Paintable
• InteractiveHighlighting
• ReadingBlock
• Voicing
• HeightSizable
• Sizable
• WidthSizable
• DelayedMutate
• AccessibleNumberSpinner
• AccessibleSlider
• AccessibleValueHandler

[jessegreenberg]

@jonathanolson are you OK with this? I wanted to run it by you because it touched Paintable, Sizable, WidthSizable, HeightSizable, DelayedMutate.

[jonathanolson]

This looks great! It didn't used to work in previous TypeScript versions, I'm very glad it works now!