Summary: This change does some refactoring in order to set up the ActivityBuffer to subscribe to a tracebus instance. It builds off of a previous change (D37528930 (72c177c337)) which publishes InodeTraceEvent objects into an InodeTraceBus, and it refactors the types used by the ActivityBuffer to also store InodeTraceEvent objects. Furthermore, this causes the trace inode retroactive command to be consistent in types used with the live trace inode command built out in (D37528930 (72c177c337)), and so we also refactor these to abstract out common formatting code shared between the two commands
Reviewed By: chadaustin, genevievehelsel
Differential Revision: D37630523
fbshipit-source-id: 8fc51478ea9f373dc718885590c5debf1ba634c8
dc3f77d92f