Introduce GC benchmarks #1759

Job	Run time
benchmark-ractor-only (head)	39s
benchmark-run-once	1m 39s
benchmark-graph	50s
test (head)	48s
benchmark-default (ruby)	13m 39s
benchmark-default (head)	14m 16s
benchmark-default (truffleruby, --excludes=knucleotide,lobsters,ruby-lsp,shipit)	13m 23s
test (ruby)	43s
test (truffleruby)	1m 47s
benchmark-ractor (head)	6m 47s
all-tests	4s
	54m 35s

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