Add `echo` keyword #8678

Job	Run time
rustfmt	5s
test (stable, x86_64-unknown-linux-gnu)	3m 51s
test-wasm	1m 28s
test (stable, x86_64-unknown-linux-musl)	6m 30s
validate	11s
lint-build	51s
test (stable, aarch64-unknown-linux-gnu)	2m 15s
test (stable, aarch64-unknown-linux-musl)	2m 40s
test (stable, x86_64-apple-darwin)	8m 4s
test (stable, x86_64-pc-windows-msvc)	5m 16s
test (stable, aarch64-apple-darwin, macos-latest, arm64, cargo, true)	5m 49s
test-projects	1m 43s
	38m 43s

Provide feedback