feat(iroh): allow to disable docs engine completely #8698

Job	Run time
Build wasm32	37s
check_semver	4m 17s
Cross Test (i686-unknown-linux-gnu)	2m 37s
Cross Build Only (armv7-linux-androideabi)	1m 3s
Cross Build Only (aarch64-linux-android)	1m 50s
Cross Build Only (x86_64-unknown-freebsd)	1m 8s
cargo deny	27s
Checking docs	1m 9s
Cross Build Only (x86_64-unknown-netbsd)	1m 9s
Checking fmt	16s
clippy_check	2m 41s
Minimal Supported Rust Version	2m 1s
Run network simulations/benchmarks	6m 55s
CI Test Suite / Tests (ubuntu-latest, stable, all)	2m 47s
CI Test Suite / Tests (ubuntu-latest, stable, none)	3m 49s
CI Test Suite / Tests (ubuntu-latest, stable, default)	2m 17s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	4m 0s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	3m 15s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	3m 53s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	3m 53s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	2m 58s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	2m 57s
	55m 59s

Provide feedback