docs(iroh-net): Update toplevel module documentation #8423

Job	Run time
cargo deny	32s
Checking fmt	13s
check_semver	4m 53s
Checking docs	2m 7s
clippy_check	3m 2s
Cross Build Only (armv7-linux-androideabi)	1m 1s
Cross Test (i686-unknown-linux-gnu)	2m 48s
Cross Build Only (aarch64-linux-android)	59s
Minimal Supported Rust Version	2m 11s
Cross Build Only (x86_64-unknown-freebsd)	1m 4s
Run network simulations/benchmarks	7m 35s
Cross Build Only (x86_64-unknown-netbsd)	1m 7s
Build wasm32	29s
CI Test Suite / Tests (ubuntu-latest, stable, all)	3m 20s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 51s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	3m 49s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	4m 0s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	3m 48s
CI Test Suite / Tests (ubuntu-latest, stable, default)	3m 2s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 38s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	3m 35s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	3m 41s
	59m 45s

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