Introduce --stats #549

Job	Run time
build / build	18m 39s
opam / build (5.3)	19m 39s
opam / build (4.14.2)	16m 14s
tests / test-local	15m 11s
tests / check-stage3	5m 57s
tests / perf-canaries	14s
tests / ocaml-smoke (fstar-src.tar.gz, ubuntu-latest)	7m 20s
tests / ocaml-smoke (fstar-src.tar.gz, ubuntu-24.04)	7m 18s
tests / binary-smoke	10s
ciok	-1s
	1h 30m 41s

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