Add PKCS#10 attributes to CSR serializer #1620

Job	Run time
Check semver compatibility	1m 2s
Validate external types appearing in public API	1m 36s
Build rustls-cert-gen as a standalone package	24s
build (macOS-latest, stable)	3m 28s
Format & clippy	5m 13s
build (ubuntu-latest, stable)	5m 53s
Documentation (stable)	1m 5s
build-windows	10m 37s
build (ubuntu-latest, beta)	5m 48s
Measure coverage	5m 51s
Documentation (nightly)	1m 0s
build (ubuntu-latest, nightly)	5m 40s
build (ubuntu-latest, stable 7 months ago)	5m 57s
	53m 34s

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