Redesign the Ractor/Knucleotide benchmark #1547

Job	Run time
benchmark-default (head)	11m 10s
test (head)	49s
test (ruby)	1m 5s
test (truffleruby)	50s
benchmark-default (truffleruby)	16m 29s
benchmark-ractor-only (ruby)	1m 8s
benchmark-ractor-only (head)	37s
benchmark-ractor (head)	6m 53s
benchmark-graph	59s
benchmark-run-once	1m 23s
benchmark-default (ruby)	11m 18s
all-tests	2s
	52m 43s

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