refactor(@angular/build): increase piscina `idleTimeout` to 4s. #1334

Job	Run time
list	25s
workflow (build-cli)	1m 26s
workflow (devkit-core-tests)	1m 12s
workflow (build-unit-tests)	2m 4s
workflow (modules-builder-tests)	1m 45s
workflow (devkit-core-tests-rerun)	1m 19s
	8m 11s

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