Redesign the Ractor/Knucleotide benchmark #1548

Job	Run time
test (ruby)	1m 1s
benchmark-default (ruby)	11m 2s
test (head)	46s
test (truffleruby)	53s
benchmark-default (truffleruby)	15m 56s
benchmark-ractor-only (head)	36s
benchmark-default (head)	10m 51s
benchmark-run-once	1m 22s
benchmark-graph	44s
benchmark-ractor (head)	6m 59s
all-tests	3s
	50m 13s

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