Add a system for dispatching notifications about contextual events, e.g. that a
particular Decl, Stmt, or Value should be highlighted. This will replace the
old system in HighlightEvent.{cpp, hpp} that was based on wxWidgets events, as
it will allow easy registration of event listeners and dispatching of events
to all listeners regardless of where they are in the window hierarchy.
Add a central ContextNotifier to TraceViewerFrame, and update the source viewer
and explanation viewer to use this ContextNotifier to listen for and publish
events requesting Decls or Stmts to be highlighted.
When showing a Value in-line in the source code viewer, send a highlight
notification for that Value. If the Value is a pointer then also send a highlight
notification for the pointee, and show a localized string that indicates a
pointer is being shown (rather than showing the raw address). Catch Value
highlight events in the state graph viewer and highlight the values if they are
shown in the graph.