release: cut the v21.2.18 release #3869

Job	Run time
list	43s
workflow (modules-builder-tests)	2m 13s
workflow (build-unit-tests)	2m 25s
workflow (devkit-core-tests)	1m 42s
workflow (devkit-core-tests-rerun)	2m 0s
workflow (build-cli)	1m 50s
	10m 53s

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