Make http-body and http-body-util dependencies optional #1087

Job	Run time
cargo-public-api-crates	1m 12s
cargo-hack	1m 14s
check-docs	50s
check	44s
cargo-deny check (advisories)	26s
cargo-deny check (bans licenses sources)	25s
test-versions (stable)	1m 39s
style	7s
test-versions (beta)	1m 40s
test-msrv	2m 48s
test-versions (nightly)	1m 45s
	12m 50s

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