Change `Callbacks` API. #2154

Job	Run time
check-cfg	21s
minimal	9s
docs	18s
msrv	52s
quickchecking	25s
rustfmt-clippy	28s
test (ubuntu-latest, 9.0, 1, 0, 0, 0, 0)	2m 0s
test-book	5s
test (ubuntu-latest, 9.0, 1, 0, 0, 1, 0)	1m 51s
test-expectations (ubuntu-latest)	46s
test (ubuntu-latest, 9.0, 1, 0, 1, 0, 0)	1m 54s
test-expectations (macos-12)	1m 23s
test (ubuntu-latest, 9.0, 1, 0, 1, 1, 0)	1m 56s
test (ubuntu-latest, 9.0, 1, 1, 0, 0, 0)	2m 6s
test (ubuntu-latest, 9.0, 1, 1, 0, 1, 0)	2m 41s
test (ubuntu-latest, 9.0, 1, 1, 1, 0, 0)	2m 14s
test (ubuntu-latest, 9.0, 1, 1, 1, 1, 0)	2m 36s
test (ubuntu-latest, 16.0, 1, 0, 0, 0, 0)	3m 6s
test (ubuntu-latest, 16.0, 1, 0, 0, 1, 0)	2m 33s
test (ubuntu-latest, 16.0, 1, 0, 1, 0, 0)	2m 33s
test (ubuntu-latest, 16.0, 1, 0, 1, 1, 0)	2m 29s
test (ubuntu-latest, 16.0, 1, 1, 0, 0, 0)	3m 2s
test (ubuntu-latest, 16.0, 1, 1, 0, 1, 0)	3m 2s
test (ubuntu-latest, 16.0, 1, 1, 1, 0, 0)	3m 10s
test (ubuntu-latest, 16.0, 1, 1, 1, 1, 0)	2m 55s
test (ubuntu-latest, 16.0, 0, 0, 1)	1m 48s
test (macos-12, 9.0, 0, 0, 0)	1m 28s
success	1s
	48m 12s

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