Add `echo` keyword #8679

Job	Run time
test-wasm	1m 35s
rustfmt	5s
lint-build	44s
test (stable, x86_64-unknown-linux-gnu)	4m 23s
test (stable, x86_64-unknown-linux-musl)	5m 48s
test (stable, aarch64-unknown-linux-gnu)	2m 17s
validate	16s
test (stable, aarch64-unknown-linux-musl)	2m 39s
test (stable, x86_64-apple-darwin)	5m 48s
test (stable, x86_64-pc-windows-msvc)	5m 34s
test (stable, aarch64-apple-darwin, macos-latest, arm64, cargo, true)	5m 51s
test-projects	1m 37s
	36m 37s

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