Separate harness implementation from the harness framework #1539

Job	Run time
benchmark-ractor (head)	12m 7s
benchmark-ractor (ruby)	12m 47s
benchmark-ractor-only (ruby)	55s
test (ruby)	1m 6s
benchmark-default (head)	12m 16s
benchmark-default (ruby)	11m 18s
benchmark-ractor-only (head)	51s
benchmark-run-once	1m 23s
test (head)	54s
benchmark-default (truffleruby)	12m 8s
test (truffleruby)	1m 11s
benchmark-graph	50s
all-tests	2s
	1h 7m 48s

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