Redesign the Ractor/Knucleotide benchmark #1559

Job	Run time
test (head)	1m 5s
test (ruby)	1m 0s
benchmark-default (head)	11m 8s
benchmark-default (ruby)	11m 44s
benchmark-ractor (head)	7m 2s
benchmark-ractor-only (head)	37s
benchmark-default (truffleruby)	14m 36s
benchmark-graph	58s
benchmark-run-once	1m 26s
test (truffleruby)	48s
all-tests	3s
	50m 27s

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