Add http3 feature to blocking client #1637

Job	Run time
Check Style	13s
Docs	1m 31s
MSRV	2m 31s
Android	29s
linux / nightly	1m 21s
unstable features	26s
linux / stable	43s
WASM	1m 4s
linux / beta	1m 11s
macOS / stable	1m 30s
windows / stable-x86_64-msvc	2m 59s
windows / stable-i686-msvc	3m 50s
windows / stable-x86_64-gnu	8m 32s
windows / stable-i686-gnu	8m 30s
feat.: default-tls disabled	53s
feat.: rustls-tls	1m 56s
feat.: rustls-tls-manual-roots	57s
feat.: native-tls	1m 5s
feat.: default-tls and rustls-tls	1m 10s
feat.: cookies	58s
feat.: blocking	1m 2s
feat.: gzip	49s
feat.: brotli	53s
feat.: deflate	51s
feat.: json	54s
feat.: multipart	59s
feat.: stream	57s
feat.: socks/default-tls	50s
feat.: socks/rustls-tls	58s
feat.: trust-dns	1m 7s
CI is green	1s
	51m 10s

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