Enable diagnostic attributes for Rust 1.78+ #4486

Job	Run time
cargo-hack	5m 21s
check	2m 27s
cargo-public-api-crates (axum)	1m 10s
cargo-public-api-crates (axum-core)	45s
check-docs	41s
cargo-public-api-crates (axum-extra)	54s
cargo-deny check (advisories)	24s
cargo-public-api-crates (axum-macros)	46s
cargo-deny check (bans licenses sources)	29s
dependencies-are-sorted	43s
Spell Check with Typos	7s
test-nightly	2m 29s
test-msrv	4m 15s
test-docs	2m 10s
test-versions (stable)	2m 46s
test-versions (beta)	4m 4s
wasm32-unknown-unknown	31s
armv5te-unknown-linux-musleabi	1m 5s
	31m 7s

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