Turn collections of `String` into collections of `Box<str>` #1656

Job	Run time
check-cfg	30s
docs	36s
msrv	2m 13s
minimal	13s
quickchecking	39s
rustfmt-clippy	44s
test (ubuntu-latest, 5.0, 1, 0, 0, 0, 0)	3m 9s
test (ubuntu-latest, 5.0, 1, 0, 0, 1, 0)	2m 35s
test (ubuntu-latest, 5.0, 1, 0, 1, 0, 0)	3m 0s
test (ubuntu-latest, 5.0, 1, 0, 1, 1, 0)	3m 12s
test (ubuntu-latest, 5.0, 1, 1, 0, 0, 0)	4m 17s
test (ubuntu-latest, 5.0, 1, 1, 0, 1, 0)	3m 55s
test (ubuntu-latest, 5.0, 1, 1, 1, 0, 0)	3m 39s
test (ubuntu-latest, 5.0, 1, 1, 1, 1, 0)	4m 30s
test (ubuntu-latest, 9.0, 1, 0, 0, 0, 0)	3m 2s
test (ubuntu-latest, 9.0, 1, 0, 0, 1, 0)	2m 53s
test (ubuntu-latest, 9.0, 1, 0, 1, 0, 0)	3m 23s
test (ubuntu-latest, 9.0, 1, 0, 1, 1, 0)	3m 37s
test (ubuntu-latest, 9.0, 1, 1, 0, 0, 0)	3m 41s
test (ubuntu-latest, 9.0, 1, 1, 0, 1, 0)	4m 4s
test (ubuntu-latest, 9.0, 1, 1, 1, 0, 0)	5m 8s
test (ubuntu-latest, 9.0, 1, 1, 1, 1, 0)	3m 53s
test (ubuntu-latest, 9.0, 0, 0, 1)	1m 58s
test (macos-latest, 9.0, 0, 0, 0)	2m 34s
test-book	27s
test-expectations (ubuntu-latest)	2m 6s
test-expectations (macos-latest)	4m 12s
	1h 14m 10s

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