fix(iroh-blobs): use async_channel instead of flume for local_pool #9394

Job	Run time
cargo deny	32s
Android Build Only (aarch64-linux-android)	1m 23s
Checking docs	1m 38s
Android Build Only (armv7-linux-androideabi)	1m 40s
Checking fmt	12s
check_semver	4m 48s
Checking typos	14s
clippy_check	2m 43s
Cross Build Only (x86_64-unknown-freebsd)	1m 12s
Cross Test (i686-unknown-linux-gnu)	3m 10s
Docker Test	8m 19s
Minimal Supported Rust Version	1m 14s
Run network simulations/benchmarks	7m 45s
Build wasm32	39s
CI Test Suite / Tests (ubuntu-latest, stable, all)	3m 9s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 34s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	4m 0s
CI Test Suite / Tests (ubuntu-latest, stable, default)	3m 6s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	4m 5s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	4m 3s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 43s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	3m 8s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	3m 25s
	1h 6m 42s

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