Remove old workaround for reentrant Property notifications

[zepumph]

From phetsims/axon#447, we now reentrantly notify Property changes as a "queue" (instead of a stack). This eliminates the need for many workarounds where we store the "old value" for later because we can't trust the oldValue provided by the property listener callback. We should get rid of these. @jonathanolson will take the lead.

For example:

scenery/js/display/SVGGradientStop.ts

Lines 32 to 34 in 589cf4a

	// As a workaround for Property deferment issues, we'll keep track of the last Color that we added a listener to, so
	// that we can clean up things Property EVEN when we don't get correct Property change notifications.
	private lastColor!: Color | null;