- display sample count and output it to json
- add proper support for totals and averages in json. When these are requested, we output stats as a dict rather than an array
#ROBOMERGE-AUTHOR: ben.woodhouse
#ROBOMERGE-SOURCE: CL 19896982 via CL 19896983 via CL 19896984
#ROBOMERGE-BOT: UE5 (Release-Engine-Staging -> Main) (v940-19807014)
[CL 19897246 by ben woodhouse in ue5-main branch]