fix(iroh): get rid of flume channels #9405

Job	Run time
Android Build Only (aarch64-linux-android)	1m 24s
Checking docs	1m 18s
Android Build Only (armv7-linux-androideabi)	1m 26s
Checking fmt	14s
cargo deny	29s
Checking typos	8s
check_semver	6m 26s
clippy_check	2m 44s
Cross Build Only (x86_64-unknown-freebsd)	1m 14s
Cross Test (i686-unknown-linux-gnu)	3m 9s
Docker Test	8m 14s
Minimal Supported Rust Version	1m 15s
Run network simulations/benchmarks	8m 42s
Build wasm32	27s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	3m 53s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	4m 8s
CI Test Suite / Tests (ubuntu-latest, stable, all)	3m 8s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	3m 59s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 34s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 40s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 44s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	3m 17s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	3m 24s
	1h 7m 57s

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