Add iterator for combinations #19497

Job	Run time
book-tests (1.10)	1h 20m 50s
doctest (1.10, ubuntu-latest)	31m 51s
book-tests (pre)	45m 0s
doctest (1.11, ubuntu-latest)	30m 33s
book-tests (nightly)	1h 3m 50s
doctest (1.12-nightly, ubuntu-latest)	36m 50s
doctest (nightly, ubuntu-latest)	31m 13s
extra-long-test	0s
doctest (1.10, ubuntu-latest, depwarn=error)	30m 7s
doctest (1.10, macOS, RPTU)	15m 26s
test (1.6, short, Linux)	20m 15s
test (1.6, long, Linux)	19m 54s
test (1.10, short, Linux)	21m 30s
test (1.10, long, Linux)	20m 1s
test (1.11, short, Linux)	23m 16s
test (1.11, long, Linux)	18m 21s
test (1.12-nightly, short, Linux)	26m 55s
test (1.12-nightly, long, Linux)	26m 42s
test (nightly, short, Linux)	1h 4m 32s
test (nightly, long, Linux)	27m 38s
test (1.10, short, Linux, RPTU, high-memory, depwarn=error)	20m 47s
test (1.10, long, Linux, RPTU, normal-memory, depwarn=error)	19m 55s
test (1.10, short, macOS, RPTU)	15m 27s
test (1.10, long, macOS, RPTU)	13m 35s
Send Slack notification on status change	0s
	11h 44m 28s

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