The goal of this ticket is to make all TicketingSystem implementations report stats using the following structure:

queues:
	execution:
		read:
			exempt:  { ... }
			lowPriority: { ... }
			normalPriority: { ... }
		write:
			exempt:  { ... }
			lowPriority: { ... }
			normalPriority: { ... }

If a category (e.g., lowPriority) does not exist, it should still be included and filled with 0s. This change will improve T2 usability and debuggability when users adjust the storage engine concurrency algorithm at runtime.