Merge pull request #488 from ruby/mvh-gc-harness #1766

Job	Run time
benchmark-ractor-only (head)	39s
benchmark-graph	50s
benchmark-default (ruby)	13m 41s
benchmark-default (head)	13m 24s
benchmark-ractor (head)	6m 44s
test (head)	48s
benchmark-run-once	1m 42s
benchmark-default (truffleruby, --excludes=knucleotide,lobsters,ruby-lsp,shipit)	13m 16s
test (ruby)	1m 0s
test (truffleruby)	1m 46s
all-tests	3s
	53m 53s

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