refactor(@angular/build): improve Vitest configuration merging #576

Job	Run time
lint	2m 31s
build	21s
build-e2e-windows	20s
e2e-windows	0s
publish-snapshots	-1s
Browser Compatibility Tests	-1s
e2e-snapshots	-1s
test	-1s
e2e	-1s
e2e-package-managers	-1s
	3m 6s

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