feat(iroh-relay): send regular pings to check the connection #12216

Job	Run time
Cross Build Only (x86_64-unknown-freebsd)	45s
Android Build Only (aarch64-linux-android)	1m 9s
Android Build Only (armv7-linux-androideabi)	1m 4s
check_semver	3m 7s
Checking fmt	20s
Cross Test (i686-unknown-linux-gnu)	1m 58s
Build wasm32	33s
cargo deny	25s
clippy_check	1m 40s
Checking docs	1m 26s
codespell	4s
Minimal Supported Rust Version	1m 33s
CI Test Suite / Tests (ubuntu-latest, stable, all)	2m 56s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 47s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 47s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	2m 14s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 2s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	2m 18s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	2m 47s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	2m 6s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 41s
netsim-integration-tests / Netsim	7m 10s
	44m 52s

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