fix(@angular/build): support merging coverage thresholds with Vitest … #2914

Job	Run time
list	21s
workflow (devkit-core-tests)	1m 18s
workflow (devkit-core-tests-rerun)	1m 23s
workflow (build-unit-tests)	2m 21s
workflow (modules-builder-tests)	1m 51s
workflow (build-cli)	1m 51s
	9m 5s

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