Add Certificate::from_pem_bundle() #1550

Job	Run time
Check Style	7s
Docs	1m 31s
linux / nightly	1m 16s
MSRV	8m 18s
Android	33s
linux / stable	53s
unstable features	30s
linux / beta	2m 32s
WASM	1m 1s
macOS / stable	1m 22s
windows / stable-x86_64-msvc	3m 26s
windows / stable-i686-msvc	4m 14s
windows / stable-x86_64-gnu	7m 21s
windows / stable-i686-gnu	6m 15s
feat.: default-tls disabled	53s
feat.: rustls-tls	52s
feat.: rustls-tls-manual-roots	50s
feat.: native-tls	1m 46s
feat.: default-tls and rustls-tls	56s
feat.: cookies	56s
feat.: blocking	1m 13s
feat.: gzip	1m 22s
feat.: brotli	2m 1s
feat.: deflate	1m 1s
feat.: json	1m 44s
feat.: multipart	54s
feat.: stream	56s
feat.: socks/default-tls	1m 44s
feat.: socks/rustls-tls	1m 19s
feat.: trust-dns	1m 7s
CI is green	1s
	58m 54s

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