Prevent exponentially large type sizes in `tuple_combinations` #939

Job	Run time
msrv	1m 20s
check format	20s
check	10s
doc	9s
check (--no-default-features)	32s
semver-checks	2m 38s
test	54s
check (--no-default-features --features use_alloc)	31s
check (--all-targets --all-features)	19s
All checks succeeded	1s
	6m 54s

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