v12 compatibility

[ben]

Working through blocking issues with v12 Testing 1.

• v12 crashes on world start if pack folders don't have a color
• Fix warnings about mergeObject and getProperty
• TextEditor.enrichHTML is always async now
  • Make sure all the places where HTML or markdown are rendered are properly wrapped in <Suspense> and an async component
  • Remove the plugin methods
• Update async rendering in Handlebars templates
  • Remove the handlebars helpers
• Reordering assets was broken because of a lingering .data
• Fix creating delve sites
• Truths
• Update adding rolls to chat messages so DSN will trigger
• Fix sidebar buttons - creating actors, placing tokens, creating folders
• Fix token-rotation HUD controls

And finally:

• Mark system.json as being tested with v12
• Update CHANGELOG.md