Add "stats" button to Toolbar to control which stats to show on each ContextNode call graph node

[Domiii]

• add new stats button to Toolbar for toggling stats information on ContextNode, when clicked...:
  • store statsMask in GraphRoot state
  • call setStatsMask on all ContextNode components
• add new Enum StatsMask
• Enum already provides several bit mask features for this. Missing operations need to be added (such as has, add and delete).
• Add a "Settings" (⚙️) button. When clicked toggles new SettingsPanel right under the Toolbar
  • Add StatsPanel to SettingsPanel
    • Allow choosing which stats to show when Stats are enabled (one checkbox per stat)
      • This should support all types of stats from StatsByContextQuery.get* functions

Explanation:

• A mask in this case refers to a "bit mask", an integer housing one boolean per individual bit.

Future Work (don't do for now)

• only dp.queryImpl.statsByContext.subscribe() when statsEnabled (can add that logic in GraphRoot.update)
  • requires extra level of bookkeeping

[MiccWan]

This could be done more easily after merging #482.