Add option to generate safe and unsafe conversions for rustified enums #2398

Job	Run time
minimal	17s
docs	23s
check-cfg	23s
msrv	53s
quickchecking	18s
rustfmt-clippy	30s
test (ubuntu-latest, 9.0, 1, 0, 0, 0, 0)	1m 45s
test-book	14s
test (ubuntu-latest, 9.0, 1, 0, 0, 1, 0)	1m 41s
test-expectations (ubuntu-latest)	44s
test (ubuntu-latest, 9.0, 1, 0, 1, 0, 0)	1m 42s
test-expectations (macos-12)	28s
test (ubuntu-latest, 9.0, 1, 0, 1, 1, 0)	2m 1s
test (ubuntu-latest, 9.0, 1, 1, 0, 0, 0)	1m 57s
test (ubuntu-latest, 9.0, 1, 1, 0, 1, 0)	1m 57s
test (ubuntu-latest, 9.0, 1, 1, 1, 0, 0)	1m 56s
test (ubuntu-latest, 9.0, 1, 1, 1, 1, 0)	1m 56s
test (ubuntu-latest, 16.0, 1, 0, 0, 0, 0)	1m 59s
test (ubuntu-latest, 16.0, 1, 0, 0, 1, 0)	1m 56s
test (ubuntu-latest, 16.0, 1, 0, 1, 0, 0)	1m 58s
test (ubuntu-latest, 16.0, 1, 0, 1, 1, 0)	1m 58s
test (ubuntu-latest, 16.0, 1, 1, 0, 0, 0)	1m 57s
test (ubuntu-latest, 16.0, 1, 1, 0, 1, 0)	1m 58s
test (ubuntu-latest, 16.0, 1, 1, 1, 0, 0)	2m 2s
test (ubuntu-latest, 16.0, 1, 1, 1, 1, 0)	1m 58s
test (ubuntu-latest, 16.0, 0, 0, 1)	1m 53s
test (macos-12, 9.0, 0, 0, 0)	1m 57s
success	1s
	38m 42s

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