add dynamic update support for FCPInformationTemplate items and actions

[sINFdorako]

Summary

• Adds updateInformationTemplateItems and updateInformationTemplateActions methods to
  dynamically update a displayed CPInformationTemplate, mirroring the existing
  updateListTemplateSections pattern for CPListTemplate.
• Fixes a bug where FCPInformationTemplate._super was never assigned, which would have prevented
  any future native-side updates.

Changes

• Swift: Added updateInformationItems/updateActions to FCPInformationTemplate, method
  channel handlers, scene delegate methods, and channel type constants
• Dart: Added mutation methods on CPInformationTemplate and public API methods on
  FlutterCarplay

Usage

flutterCarplay.updateInformationTemplateItems(
  elementId: template.uniqueId,
  items: [CPInformationItem(title: 'ETA', detail: '5 min')],
);

flutterCarplay.updateInformationTemplateActions(
  elementId: template.uniqueId,
  actions: [CPTextButton(title: 'Cancel', onPress: () {})],
);