refactor: move docs engine into iroh-docs (#2343) #8475

Job	Run time
cargo deny	30s
check_semver	4m 59s
Checking docs	1m 56s
Checking fmt	12s
clippy_check	2m 43s
Cross Build Only (armv7-linux-androideabi)	1m 8s
Cross Test (i686-unknown-linux-gnu)	2m 32s
Minimal Supported Rust Version	1m 59s
Cross Build Only (aarch64-linux-android)	1m 6s
Cross Build Only (x86_64-unknown-freebsd)	1m 8s
Run network simulations/benchmarks	7m 25s
Cross Build Only (x86_64-unknown-netbsd)	1m 10s
Build wasm32	27s
CI Test Suite / Tests (ubuntu-latest, stable, all)	2m 25s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	3m 55s
CI Test Suite / Tests (ubuntu-latest, stable, none)	2m 7s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	3m 56s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 37s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	3m 52s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 3s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	2m 53s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 53s
	54m 56s

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