Upgrade botan to 0.11 #1691

Job	Run time
Build rustls-cert-gen as a standalone package	26s
build (macOS-latest, stable)	3m 36s
build (ubuntu-latest, stable)	6m 47s
build-windows	13m 18s
Validate external types appearing in public API	1m 41s
Measure coverage	6m 37s
build (ubuntu-latest, beta)	7m 0s
Format & clippy	6m 24s
build (ubuntu-latest, nightly)	6m 58s
build (ubuntu-latest, stable 7 months ago)	7m 0s
Documentation (stable)	1m 6s
Documentation (nightly)	1m 15s
Check semver compatibility	54s
	1h 3m 2s

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