refactor(@angular/build): modularize unit-test builder with runner-sp… #726

Job	Run time
list	28s
workflow (devkit-core-tests-rerun)	34s
workflow (devkit-core-tests)	32s
workflow (build-cli)	29s
workflow (modules-builder-tests)	29s
workflow (build-unit-tests)	27s
	2m 59s

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