fix: Try improving `relay_datagram_send_channel()` (#3118) #12183

Job	Run time
Cross Build Only (x86_64-unknown-freebsd)	44s
Android Build Only (aarch64-linux-android)	1m 11s
Android Build Only (armv7-linux-androideabi)	1m 5s
Build wasm32	34s
Checking docs	1m 11s
Checking fmt	20s
clippy_check	2m 16s
check_semver	3m 39s
Cross Test (i686-unknown-linux-gnu)	1m 59s
cargo deny	26s
codespell	4s
Minimal Supported Rust Version	1m 10s
CI Test Suite / Tests (ubuntu-latest, stable, all)	2m 8s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 32s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 14s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	2m 20s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	2m 15s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	2m 8s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	2m 8s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 8s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	2m 9s
netsim-integration-tests / Netsim	5m 28s
	40m 9s

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