refactor: remove req_res_handler() #1707

Job	Run time
cargo_fmt	8s
cargo_test_msrv	2m 48s
cargo_test (ubuntu-20.04)	35s
build_for_mac (x86_64-apple-darwin)	5m 51s
cargo_test (macOS-11)	1m 38s
build_for_mac (aarch64-apple-darwin)	5m 26s
docker	5m 48s
cross_build (aarch64-unknown-linux-musl)	3m 24s
cross_build (arm-linux-androideabi)	3m 41s
cross_build (arm-unknown-linux-musleabi)	3m 28s
cross_build (arm-unknown-linux-musleabihf)	3m 27s
cross_build (armv5te-unknown-linux-musleabi)	3m 36s
cross_build (armv7-linux-androideabi)	3m 39s
cross_build (armv7-unknown-linux-musleabihf)	3m 39s
cross_build (armv7-unknown-linux-musleabi)	3m 31s
cross_build (i586-unknown-linux-musl)	3m 24s
cross_build (i686-linux-android)	3m 31s
cross_build (i686-unknown-linux-musl)	3m 30s
cross_build (x86_64-linux-android)	3m 30s
cross_build (x86_64-pc-windows-gnu)	3m 42s
cross_build (x86_64-unknown-linux-musl)	3m 22s
linux_operational_test	23s
release_if_tag_exits	5s
	1h 12m 6s

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