Separate harness implementation from the harness framework #1528

Job	Run time
benchmark-ractor (ruby)	13m 8s
benchmark-ractor-only (ruby)	57s
benchmark-ractor (head)	12m 20s
benchmark-ractor-only (head)	44s
benchmark-default (head)	11m 17s
benchmark-default (truffleruby)	14m 25s
benchmark-default (ruby)	11m 7s
test (truffleruby)	1m 15s
benchmark-graph	50s
benchmark-run-once	1m 31s
test (ruby)	1m 0s
test (head)	1m 4s
all-tests	4s
	1h 9m 42s

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