Raised supported ecmaVersion from es2018 to es2021 #1616

Job	Run time
build	3m 25s
check-and-lint	30s
adapter-tests (16.x, ubuntu-latest)	4m 9s
adapter-tests (16.x, windows-latest)	5m 7s
adapter-tests (16.x, macos-latest)	5m 5s
adapter-tests (18.x, ubuntu-latest)	4m 8s
adapter-tests (18.x, windows-latest)	9m 5s
adapter-tests (18.x, macos-latest)	5m 3s
adapter-tests (20.x, ubuntu-latest)	4m 8s
adapter-tests (20.x, windows-latest)	6m 6s
adapter-tests (20.x, macos-latest)	5m 1s
deploy	0s
	51m 47s

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