Improve debug str generator #2571

Job	Run time
docs	28s
msrv	52s
check-cfg	22s
minimal	16s
quickchecking	19s
rustfmt-clippy	28s
test-book	7s
test-expectations (ubuntu-latest)	49s
test (ubuntu-latest, 9.0, 1, 0, 0, 0, 0)	1m 42s
test-expectations (macos-12)	1m 2s
test (ubuntu-latest, 9.0, 1, 0, 0, 1, 0)	1m 48s
test (ubuntu-latest, 9.0, 1, 0, 1, 0, 0)	1m 43s
test (ubuntu-latest, 9.0, 1, 0, 1, 1, 0)	1m 43s
test (ubuntu-latest, 9.0, 1, 1, 0, 0, 0)	2m 6s
test (ubuntu-latest, 9.0, 1, 1, 0, 1, 0)	2m 20s
test (ubuntu-latest, 9.0, 1, 1, 1, 0, 0)	2m 6s
test (ubuntu-latest, 9.0, 1, 1, 1, 1, 0)	2m 13s
test (ubuntu-latest, 16.0, 1, 0, 0, 0, 0)	3m 59s
test (ubuntu-latest, 16.0, 1, 0, 0, 1, 0)	4m 10s
test (ubuntu-latest, 16.0, 1, 0, 1, 0, 0)	4m 10s
test (ubuntu-latest, 16.0, 1, 0, 1, 1, 0)	4m 4s
test (ubuntu-latest, 16.0, 1, 1, 0, 0, 0)	4m 47s
test (ubuntu-latest, 16.0, 1, 1, 0, 1, 0)	4m 56s
test (ubuntu-latest, 16.0, 1, 1, 1, 0, 0)	4m 34s
test (ubuntu-latest, 16.0, 1, 1, 1, 1, 0)	5m 2s
test (ubuntu-latest, 16.0, 0, 0, 1)	1m 49s
test (macos-12, 9.0, 0, 0, 0)	1m 29s
success	1s
	59m 25s

Provide feedback