"Tier 1" features for Voicing related to the Voicing Toolbar

[jessegreenberg]

This issue is to implement what is needed for scaling "Tier 1" Voicing features.

From a design document, this includes:

Play Overview (available from Voicing Toolbar). (Relationship to Interactive Description: Equivalent to Sim Overview, must not refer to Play Area or Control Area.)

Play Details (available from Voicing Toolbar). (Relationship to Interactive Description: Ideally same as Essential Big-Picture Details.)

Play Hint (available from Voicing Toolbar). (Relationship to Interactive Description: Same as Interaction Hint.)

Related to #993, where we are considering Voicing overlap with ScreenSummaryContent.

[jessegreenberg]

In phetsims/trig-tour#108, we discussed using the same string for Voicing screen summary content and PDOM screen summary content. That would let us use the same string and also have one setter for both Voicing and Interactive Description content in ScreenSummaryContent.

[jessegreenberg]

Some scratch code while brainstorming during meeting:

      screenSummaryContent: new ScreenSummaryContent( {
        playAreaContent: [
          ModelsOfTheHydrogenAtomStrings.a11y.spectraScreen.screenSummary.playAreaStringProperty,
        ],
        controlAreaContent: [
          ModelsOfTheHydrogenAtomStrings.a11y.spectraScreen.screenSummary.controlAreaStringProperty,
        ],
        interactionHintContent: [
          ModelsOfTheHydrogenAtomStrings.a11y.spectraScreen.screenSummary.interactionHintStringProperty,
        ],

        // Optional overrides for Voicing content, if necessary
        voicingPlayAreaContent: [
          ModelsOfTheHydrogenAtomStrings.a11y.spectraScreen.screenSummary.voicingPlayAreaStringProperty
        ]
      } ),