refactor(@angular/build): provide private factory API for internal co… #1453

Job	Run time
list	27s
workflow (devkit-core-tests)	1m 10s
workflow (modules-builder-tests)	1m 33s
workflow (build-unit-tests)	2m 13s
workflow (build-cli)	1m 37s
workflow (devkit-core-tests-rerun)	1m 13s
	8m 13s

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