fix(iroh-blobs): use async_channel instead of flume for local_pool #9388

Job	Run time
cargo deny	27s
Checking docs	1m 13s
Checking fmt	9s
Android Build Only (aarch64-linux-android)	1m 21s
Android Build Only (armv7-linux-androideabi)	1m 24s
check_semver	1m 49s
Checking typos	4s
clippy_check	2m 3s
Cross Build Only (x86_64-unknown-freebsd)	1m 20s
Cross Test (i686-unknown-linux-gnu)	2m 6s
Docker Test	1m 57s
Minimal Supported Rust Version	1m 17s
Run network simulations/benchmarks	42s
Build wasm32	33s
CI Test Suite / Tests (ubuntu-latest, stable, all)	38s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	1m 54s
CI Test Suite / Tests (ubuntu-latest, stable, none)	1s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	1s
CI Test Suite / Tests (ubuntu-latest, stable, default)	39s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	1m 53s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	2m 6s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	1s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 6s
	25m 44s

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