Stats refactor

[nirandaperera]

As discussed today in a meeting, we will do the following.

• Use the same stats object everywhere
• During object creation, if the args contains an object that contains stats, borrow the stats object from that arg. If there are multiple objects, its up to the class to determine which stats to use (ideally all should point to the same stats instance)

Depends on:

• Refactor memory resource ownership and type safety #985
• Remove memory resources from Statistics #1003

Todo:

• Make stats object using a factory method Initial stats cleanup #1009
• Use the same stats object everywhere Initial stats cleanup #1009
• Pass stats to Communicator

Post merge:

• Add coarse comms metrics #999