Add lower speed limit to full async body retrievals. #1552

Job	Run time
Check Style	8s
Docs	2m 18s
MSRV	5m 41s
linux / nightly	2m 22s
Android	44s
linux / stable	53s
unstable features	24s
linux / beta	1m 55s
macOS / stable	1m 38s
WASM	1m 4s
windows / stable-x86_64-msvc	4m 57s
windows / stable-i686-msvc	4m 51s
windows / stable-x86_64-gnu	6m 55s
windows / stable-i686-gnu	7m 44s
feat.: default-tls disabled	53s
feat.: rustls-tls	54s
feat.: rustls-tls-manual-roots	58s
feat.: native-tls	55s
feat.: default-tls and rustls-tls	1m 1s
feat.: cookies	59s
feat.: blocking	2m 10s
feat.: gzip	57s
feat.: brotli	1m 49s
feat.: deflate	1m 55s
feat.: json	59s
feat.: multipart	54s
feat.: stream	56s
feat.: socks/default-tls	56s
feat.: socks/rustls-tls	1m 51s
feat.: trust-dns	1m 9s
CI is green	1s
	1h 0m 51s

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