Separate harness implementation from the harness framework #1516

Job	Run time
benchmark-ractor (ruby)	12m 56s
benchmark-ractor (head)	12m 15s
test (truffleruby)	55s
test (ruby)	1m 8s
benchmark-ractor-only (ruby)	58s
test (head)	59s
benchmark-ractor-only (head)	52s
benchmark-default (truffleruby)	15m 57s
benchmark-graph	56s
benchmark-default (head)	10m 52s
benchmark-default (ruby)	10m 55s
benchmark-run-once	7s
all-tests	4s
	1h 8m 54s

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