Separate harness implementation from the harness framework #1517

Job	Run time
test (truffleruby)	1m 8s
test (head)	59s
benchmark-default (ruby)	11m 2s
benchmark-ractor (ruby)	12m 47s
test (ruby)	59s
benchmark-default (truffleruby)	13m 55s
benchmark-default (head)	11m 1s
benchmark-ractor-only (ruby)	56s
benchmark-ractor-only (head)	47s
benchmark-graph	1m 0s
benchmark-ractor (head)	12m 23s
benchmark-run-once	1m 39s
all-tests	3s
	1h 8m 39s

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