Improve `debug_handler` on tuple response types #3974

Job	Run time
check-docs	33s
cargo-hack	10m 51s
check	46s
cargo-public-api-crates (axum)	1m 33s
cargo-public-api-crates (axum-core)	1m 23s
cargo-deny check (advisories)	31s
cargo-public-api-crates (axum-extra)	59s
dependencies-are-sorted	19s
Spell Check with Typos	7s
cargo-deny check (bans licenses sources)	31s
cargo-public-api-crates (axum-macros)	46s
armv5te-unknown-linux-musleabi	1m 19s
test-nightly	2m 8s
test-docs	4m 18s
test-msrv	13m 32s
test-versions (stable)	3m 16s
wasm32-unknown-unknown	24s
test-versions (beta)	1m 48s
	45m 4s

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