feat(prof): add aggregate metric output in Bencher JSON format

[jonathanpwang]

I tested locally it works with https://bencher.dev/docs/how-to/track-custom-benchmarks/

[github-actions]

group	app.proof_time_ms	app.cycles	app.cells_used	leaf.proof_time_ms	leaf.cycles	leaf.cells_used
verify_fibair	(-31 [-1.4%]) 2,184	513,767	18,710,224	-	-	-
fibonacci_program	(-51 [-1.0%]) 5,286	1,500,095	51,485,080	-	-	-
regex_program	(-72 [-0.5%]) 15,303	1,914,103	165,455,373	-	-	-
ecrecover_program	(+12 [+0.5%]) 2,598	284,567	15,055,723	-	-	-

Commit: ad3e111

Benchmark Workflow