fix(iroh-net): return `Poll::Read(Ok(n))` when we have no relay URL o… #8524

Job	Run time
Cross Build Only (armv7-linux-androideabi)	1m 4s
Build wasm32	33s
Cross Build Only (aarch64-linux-android)	1m 1s
Cross Test (i686-unknown-linux-gnu)	3m 33s
Cross Build Only (x86_64-unknown-freebsd)	1m 9s
Cross Build Only (x86_64-unknown-netbsd)	1m 8s
cargo deny	39s
Checking docs	1m 51s
check_semver	4m 35s
Checking fmt	7s
clippy_check	3m 3s
Minimal Supported Rust Version	1m 16s
Run network simulations/benchmarks	8m 2s
CI Test Suite / Tests (ubuntu-latest, stable, all)	2m 25s
CI Test Suite / Tests (ubuntu-latest, stable, none)	3m 18s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 44s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	3m 54s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 4s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	3m 41s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	2m 54s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	3m 56s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 52s
	56m 49s

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