Adds interface hooks to allow plugins (and c++) to register "development/debugging" tools
These tools appear in a new Development/Debugging Tools dock, and provide a unified handling and place for these tools in the UI.
The intention here is that specialised development/debugging tools will be moved to this common interface, e.g.

• Network logger
• First aid style Python local variables inspector
• Startup time debugging tools
• Layer load and rendering time debugging tools ... ?

Here's an example demo showing a "Python locals" dev tool: