Add `echo` keyword #8529

Job	Run time
rustfmt	10s
test-wasm	1m 24s
test (stable, x86_64-unknown-linux-gnu)	1m 23s
test (stable, x86_64-unknown-linux-musl)	2m 0s
lint-build	31s
validate	10s
test (stable, aarch64-unknown-linux-gnu)	1m 34s
test (stable, aarch64-unknown-linux-musl)	1m 33s
test (stable, x86_64-apple-darwin)	3m 4s
test (stable, x86_64-pc-windows-msvc)	3m 6s
test (stable, aarch64-apple-darwin, macos-latest, arm64, cargo, true)	1m 32s
test-projects	0s
	16m 27s

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