Add script to diff zjit stats from output csv #1682

Job	Run time
benchmark-graph	48s
benchmark-run-once	1m 35s
benchmark-ractor-only (head)	40s
benchmark-ractor (head)	6m 50s
test (ruby)	54s
benchmark-default (ruby)	13m 27s
test (truffleruby)	1m 50s
benchmark-default (truffleruby, --excludes=knucleotide,lobsters,ruby-lsp,shipit)	13m 13s
benchmark-default (head)	14m 2s
test (head)	53s
all-tests	4s
	54m 16s

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