refactor(iroh): use boxed client to get rid of the C type parameter #8682

Job	Run time
Cross Test (i686-unknown-linux-gnu)	9s
Cross Build Only (armv7-linux-androideabi)	8s
Cross Build Only (aarch64-linux-android)	9s
Cross Build Only (x86_64-unknown-freebsd)	8s
Checking fmt	5s
Cross Build Only (x86_64-unknown-netbsd)	7s
check_semver	7s
Build wasm32	5s
cargo deny	16s
Checking docs	16s
clippy_check	9s
Minimal Supported Rust Version	14s
Run network simulations/benchmarks	9s
CI Test Suite / Tests (ubuntu-latest, stable, all)	11s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	30s
CI Test Suite / Tests (ubuntu-latest, stable, none)	12s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	26s
CI Test Suite / Tests (ubuntu-latest, stable, default)	15s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	24s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	12s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	12s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	14s
	4m 38s

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