feat(iroh-relay): send regular pings to check the connection #12164

Job	Run time
Cross Build Only (x86_64-unknown-freebsd)	43s
Android Build Only (aarch64-linux-android)	1m 5s
check_semver	2m 50s
Cross Test (i686-unknown-linux-gnu)	1m 57s
Android Build Only (armv7-linux-androideabi)	1m 10s
Build wasm32	34s
cargo deny	27s
Checking docs	1m 10s
Checking fmt	22s
clippy_check	56s
codespell	4s
Minimal Supported Rust Version	1m 3s
CI Test Suite / Tests (ubuntu-latest, stable, all)	2m 59s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 50s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	2m 13s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	1m 37s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 48s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	2m 11s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 1s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	1m 1s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 57s
netsim-integration-tests / Netsim	2m 55s
	36m 53s

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